Grey pixelated screen on startup?

For a few seconds when I wake or boot up my 15' Retina Macbook Pro (mid 2012) the screen shows a pixelated grey screen - kind of white noise. It doesn't last long, only a few seconds, then OS X (10.10.1) boots up (but always with the wrong screen resolution - but I don't imagine these are related issues?). It would seem to be like that's a graphic card problem? Will a fresh install of OS X fix this do you think? (I'm having trouble reinstalling OS X but I'll save that for another time)
Thanks!

The static that shows up briefly on the screen at start-up is harmless: it's showing up on some/many MBP's for years now. Some claim it can be solved (temporarily) by resetting PRAM and SMC, but I don't even bother anymore.
Starting up in de wrong resolution is odd though. So in your case, a PRAM might be a thing to try.

Similar Messages

Kernel panics & grey debug screen at startup

Tiger (10.4.10) on a 2 GHz Mac mini (Intel) and Airport as well as IPv6 disabled.
Not sure which torrent client I installed first but I think it was Transmission and everything was fine. Then I installed Azureus on the advise of a friend and started getting kernel panics. Switched back to Transmission and KPs continued. Soon I started getting them with just running Safari or even Firefox.
Next there was a Mac OS upgrade (10.4.11 and a couple other things) and the machine would not even start up anymore. Always got a grey debug screen with msg to press powerbutton.
Tried doing an archive and install and it failed twice.
Tried doing a clean install (OS only) on external 30GB USB 2.0 HD and it failed as well.
Apple Support and Apple store were clueless.
At least the genius was able to boot with their troubleshooting HD and run Disk Warrior which found a couple minor issues and I was able to see that my data was stull there. Unfortunately the 30gb HD was too small to copy my user folder (86gb).
Went and bought an external 320gb firewire disk and tried to do a clean install and it failed.
Called Apple again and suspected bad DVD media. They sent replacement disks and they failed as well.
Ran Apple Hardware Test and it found bad memory (?) with 2x 1GB Corsair sticks. I even tried them individually. That memory has worked since August 2007 until I started seeing the kernel panics in December. What are the odds of both SODIMMs going bad at the same time ? Could a bad app cause memory to go bad ? I doubt it.
with 2 GB Corsair memory: 4MEM/4/40000000:2c02fd60
Swapped original 2x 512 MB Apple sticks in and AHT found another error.
with 1 GB Apple memory: 4SNS/1/40000000:TAOP
From other forum posts I found that 4MEM usually indicates a memory or system board issue while 4SNS seems to indicate a sensor issue, but that could have been due to unplugged (termal?) cable in front of mini due to the need to swap memory in and out for testing.
What gives ?
I was however, able to install now on external FW disk and copy my user folder to it as well.
So this indicates a problem with 3rd party mem but there may be something else wrong with mini system board or Apple mem as well.
TX

::UPDATE::
Okay, I eventually got my iMac to start up successfully, without crashing after logging in. But I still thought there was something wrong so I booted from the Apple Hardware Test CD that came with my computer and I got yet ANOTHER Kernel Panic! Here is what it said:
Kernel Panic Message:
DEFAULT CATCH!, code=300 at %SRR0: 000352d4 %SRR1: 00003030
Apple PowerMac4,2 4.3.5f1 BootROM built on 03/16/02 at 21:45:18
Copyright 1994-2002 Apple Computer, Inc.
All Ri
DEFAULT CATCH!, code=300 at %SRR0: ff84750c %SSR1: 0000b030
ok
0>
DEFAULT CATCH!, code=300 at SSR0: ff84750c %SSR1:_
This message appeared soon after it began testing the memory. The result of the test were as follows:
Test Results:
Airport Passed
Logic Board Passed
Mass Storage Passed
Memory In Progress
Modem Device Found
Video RAM Has not been run yet
And now it is back to not booting up at all!
Does anyone have any suggestions based on the new kernel panic message?
Thank you for your help.
Message was edited by: rrm74001

My Mac book pro shows this grey distorted screen during startup. Any ideas?

Looks like the above for a few minutes but then will go to the login screen like normal and work perfectly.

Reset PRAM. http://support.apple.com/kb/PH4405
Best.

Powerbook freezes at grey screen on startup

I have a 3+ year old Powerbook running 10.4.9 that won't go past the grey apple screen on startup. It pretty much spins indefinitely. I thought it might be a failing hard drive, but I'm not sure after the tests I've done. The drive is 80GB (74.53 GB capacity), with 7.99 GB available space. The drive itself is not as old as the laptop; it was replaced by Apple about a year ago. I have tried the following (with restart attempts in between):
*Zap PRAM
*Reset PMU
*Start up in safe mode (works normally, as far as safe mode is concerned)
*Ran AHT, found bad RAM module, removed module, ran AHT twice and found no other errors
*Startup in single user mode, run fsck, volume "appears to be OK"
*Attach to another PPC 10.4 machine to try to do a backup of files (mounts, works for a while, then crashes the "target" machine (iMac G5 20" 10.4.9))
*Tried to backup to iMac w/drag and drop, migration assistant (both firewire) and via direct Ethernet connection. Always works for a bit then crashes, forcing a manual shut down of iMac
*Startup from external FW drive w/OS X, ran Disk Utility, no problems found on internal HD
*Startup in open firmware, reset NVRAM
*Ran DiskWarrior 4.0, rebuilt directory
*S.M.A.R.T. status is normal/verified
Any suggestions, ideas would be much appreciated. I am really at a loss and very much want to fix this. Thank you.
-Amy
1.25 GHz AlBook 15 Mac OS X (10.4.9) 1 GB RAM

The problem may be the hard drive is too full. We have found that you don't want your hard drive to be more than 85% full. At last count 8 GB of 80 GB is 90% full.

New iMac is stuck on grey apple screen after restart from Migration Assistant

New iMac is stuck on grey apple screen after startup. It is a 3.4GHz Quad-core Intel Core i5 running OS 10.9.4. The problem occurred after a migration from my older 2009 iMac which is running Snow Leopard 10.6.6. When the restart occurred from Migration Assistant, the new computer will not boot up to the login screen. Disk utility did not solve problem. Followed instructions for a soft reinstall of Mavericks but that also did not solve problem. Any suggestions?

Take each of these steps that you haven't already tried. Stop when the problem is resolved.
Step 1
The first step in dealing with a startup failure is to secure the data. If you want to preserve the contents of the startup drive, and you don't already have at least one current backup, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data that has changed since the last backup, you can skip this step.
There are several ways to back up a Mac that is unable to start. You need an external hard drive to hold the backup data.
a. Start up from the Recovery partition, or from a local Time Machine backup volume (option key at startup.) When the OS X Utilities screen appears, launch Disk Utility and follow the instructions in this support article, under “Instructions for backing up to an external hard disk via Disk Utility.” The article refers to starting up from a DVD, but the procedure in Recovery mode is the same. You don't need a DVD if you're running OS X 10.7 or later.
b. If Step 1a fails because of disk errors, and no other Mac is available, then you may be able to salvage some of your files by copying them in the Finder. If you already have an external drive with OS X installed, start up from it. Otherwise, if you have Internet access, follow the instructions on this page to prepare the external drive and install OS X on it. You'll use the Recovery installer, rather than downloading it from the App Store.
c. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, start the non-working Mac in target disk mode. Use the working Mac to copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.
d. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.
Step 2
If the startup process stops at a blank gray screen with no Apple logo or spinning "daisy wheel," then the startup volume may be full. If you had previously seen warnings of low disk space, this is almost certainly the case. You might be able to start up in safe mode even though you can't start up normally. Otherwise, start up from an external drive, or else use the technique in Step 1b, 1c, or 1d to mount the internal drive and delete some files. According to Apple documentation, you need at least 9 GB of available space on the startup volume (as shown in the Finder Info window) for normal operation.
Step 3
Sometimes a startup failure can be resolved by resetting the NVRAM.
Step 4
If you use a wireless keyboard, trackpad, or mouse, replace or recharge the batteries. The battery level shown in the Bluetooth menu item may not be accurate.
Step 5
If there's a built-in optical drive, a disc may be stuck in it. Follow these instructions to eject it.
Step 6
Press and hold the power button until the power shuts off. Disconnect all wired peripherals except those needed to start up, and remove all aftermarket expansion cards. Use a different keyboard and/or mouse, if those devices are wired. If you can start up now, one of the devices you disconnected, or a combination of them, is causing the problem. Finding out which one is a process of elimination.
Step 7
If you've started from an external storage device, make sure that the internal startup volume is selected in the Startup Disk pane of System Preferences.
Start up in safe mode. Note: If FileVault is enabled, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Post for further instructions.
Safe mode is much slower to start and run than normal, and some things won’t work at all, including wireless networking on certain Macs.
The login screen appears even if you usually log in automatically. You must know the login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
When you start up in safe mode, it's normal to see a dark gray progress bar on a light gray background. If the progress bar gets stuck for more than a few minutes, or if the system shuts down automatically while the progress bar is displayed, the startup volume is corrupt and the drive is probably malfunctioning. In that case, go to Step 11. If you ever have another problem with the drive, replace it immediately.
If you can start and log in in safe mode, empty the Trash, and then open the Finder Info window on the startup volume ("Macintosh HD," unless you gave it a different name.) Check that you have at least 9 GB of available space, as shown in the window. If you don't, copy as many files as necessary to another volume (not another folder on the same volume) and delete the originals. Deletion isn't complete until you empty the Trash again. Do this until the available space is more than 9 GB. Then restart as usual (i.e., not in safe mode.)
If the startup process hangs again, the problem is likely caused by a third-party system modification that you installed. Post for further instructions.
Step 8
Launch Disk Utility in Recovery mode (see Step 1.) Select the startup volume, then run Repair Disk. If any problems are found, repeat until clear. If Disk Utility reports that the volume can't be repaired, the drive has malfunctioned and should be replaced. You might choose to tolerate one such malfunction in the life of the drive. In that case, erase the volume and restore from a backup. If the same thing ever happens again, replace the drive immediately.
This is one of the rare situations in which you should also run Repair Permissions, ignoring the false warnings it may produce. Look for the line "Permissions repair complete" at the end of the output. Then restart as usual.
Step 9
If the startup device is an aftermarket SSD, it may need a firmware update and/or a forced "garbage collection." Instructions for doing this with a Crucial-branded SSD were posted here. Some of those instructions may apply to other brands of SSD, but you should check with the vendor's tech support.
Step 10
Reinstall the OS. If the Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade.
Step 11
Do as in Step 9, but this time erase the startup volume in Disk Utility before installing. The system should automatically restart into the Setup Assistant. Follow the prompts to transfer the data from a Time Machine or other backup.
Step 12
This step applies only to models that have a logic-board ("PRAM") battery: all Mac Pro's and some others (not current models.) Both desktop and portable Macs used to have such a battery. The logic-board battery, if there is one, is separate from the main battery of a portable. A dead logic-board battery can cause a startup failure. Typically the failure will be preceded by loss of the settings for the startup disk and system clock. See the user manual for replacement instructions. You may have to take the machine to a service provider to have the battery replaced.
Step 13
If you get this far, you're probably dealing with a hardware fault. Make a "Genius" appointment at an Apple Store, or go to another authorized service provider.

My macbook pro wont get past the grey screen at startup. Help!!

After doing a run of the mill software update on my macbook pro (running snow leopard) it froze during the "moving items into place" stage. I forced a shut down and now it wont get past the grey screen with apple logo and spinning wheel. I have tried booting from the original DVD but it still freezes. When I boot it in verbose mode it seems to stop at "jnl: unknown-dev: update_fs_block: error reading fs block # 3597880! (ret 5)", the Apple AHCD Disk Queue manager :: set power state is timing out and there is a disk I/O error. I have tried to reset the power manager (not sure if it worked or not) and I have also tried clearing the PRAM (again, not sure of that worked). When I try to look at the hard drive using target mode on my imac the hard drive doesn't come up but the DVD does. I'm concerned that my hard drive is fried. Any suggestions?

It would help to state in your post which remedies you tried that didn't work.
Start here > OS X Lion: If you see a gray screen at startup
If nothing there helped, try Starting up in Safe Mode
Safe Mode deletes some system caches that may help.
A Safe Mode boot takes longer than a normal boot so be patient. Once you are in Safe Mode, click Restart from the Apple menu.
If a Safe Mode boot didn't work, since your Mac has OS X v10.7 installed, restart your Mac while holding down the Command + R keys so you can access OS X Recovery built in utilities. The startup disk may need repairing.
Tip: Hold down the Eject key while starting up your Mac to eject a disc.

Persistent grey screen on startup.

I own a late 2011 MacBook Pro running osx mavericks. Had it for two years with no problems. In early January of this year the macbook would crash whenever I opened photoshop or other programs like iMovie or photobooth. The only way to get it to function again was to hard restart the laptop. And Even then sometimes I would get the grey screen on start up and hear three beeps. I Went to the Genius Bar and the employee reseated the RAM and the laptop functioned well for a week. When the persistent grey screen appeared again, the genius employee erased all my storage, with my permission, reset my operation system completely. Even still I get the grey screen and the laptop doesn't make it to the login. What should I do to fix it? Would buy info new ram solve the problem? If tried pessimg shift and running in safe mode but I just get a blue screen and am forced to hard reset.

Hi there friends
I don't have apple help in my city
I'm using MBP as desktop removed battery due to batter sensors issue.
It is late 2011.
It started with no startup tone chime than I set nvram so startup tone came but the persisting issue is grey bar at the startup blow apple logo that takes 20 min almost and after completion MBP turns off and requires manual turn on and upon re turning on again that grey bat appears same fasion.
Some one told me to go to safe mode and apply some changes but I can't go to safe mode with shift key startup login Id password bar appears and constant shift key press interrupts and again grey bat appears.
I don't know how to disable startup password and how to disable vault.
Please help me in
How to get into safe mode
How to get rid of grey bar on startup
My discs are working well I checked in recovery.
Please help me even I don't have disc
And if you could help me in how to open a USB net modem.with the MBP having same issues as with mine
Thanks

TS2570 Grey screen on startup...

I am using 2008 White Macbook with OSX lion running on it. Recently I tried to update the OS and then I started getting a folder with question mark on startup. After that I started getting a continuous grey screen on startup. I tried various options like command + option + P + Q, then Command + R, etc. but did not get any response. After that I pressed option key on startup then there was a response. A lock icon appeared on screen asking for a password. I tried the MacBook password and it is not taking that password as well. I tired all the passwords I remembered but nothing worked. My cd drive is not working and also I do not have original OS disks with me now. The apple service centre told that they can resolbe it as it is a vintage model. I called apple care but they are asking 29 $ for a call Which is ridiculou. Pl. help me

Does the lock screen look like the one on this page…
http://osxdaily.com/2014/01/06/set-firmware-password-mac/
That is an EFI password - it stops the firmware accepting ANY startup commands so you cannot boot from other media or use the startup keys to get into recovery mode, single user mode, target disk mode etc.
If you can't remember the password you will need to remove the battery & leave it unpowered for a few days. If you are lucky it will reset. If it doesn't reset you need to open the case & remove the internal clock battery. Not something anyone should do without the skills to work on electronics - take it to an Apple Store or an Apple approved service centre would be my advice.
It is also possible that you have Filevault password instead of an EFI password - did you need to enter a password after every reboot before the OS failed. This shouldn't be confused with a normal user account password.
If you have Filevault enabled you can still try booting into recovery mode, but you must enter the password to repair the boot disk.
The 'question mark folder' means it cannot find an OS that is bootable - it need to be repaired but you can't get to recovery mode without the EFI password - a catch 22 situation.
Since you have no install disks or other ways to boot it seems you are probably not going to be able to fix this. If you have another Mac you could try to download 10.7 & create a USB install disk & use that to try to repair the Mac, but it seems unlikely since it appears to have a firmware password.

Grey screen on startup resolution.

Hi All
I have been getting the grey (although I call it blue) screen on startup over the past year. I have an intel imac with the latest version of snow leopard on it. I've tried everything suggested in the forums, including rebuilding my machine from scratch (not a trivial task for production music software / hardware).
One thing I can't understand is why my machine has this issue with a clean install, and no periphirals attached. My machine has been in the Apple shop and has been verified as ok.
I have contacted the Australian Consumers Comission and think that this comes under the expectation of durability, which can apply even if the manufacturers warranty has expired.
I've invested a lot of time and money into Apple hardware and software and would have expected a resolution to this problem by now. Having to manually power off my machine 3 to 4 times in a row to get it to boot propery is obviously going to impact on the lifetime of my harddrives.
I'd like as much feedback and personal experience that people have had with this issue before continuing any further.

I boot my mac with verbose settings on, I get the normal beep, then I get all the normal output (same output as when it boots ok), then a blue / grey screen. It hangs for around 15 mins. After that it continues to boot until it's logged in, but then there is no interaction with the mouse or keyboard. I can see the mouse pointer moving around, but can't click on anything. If I have the time I will log in from another machine and perform a normal shutdown, otherwise it's a hard reset.
I've tried resetting the nvram, repairing permissions, checking the hard drive, rebuilding the machine, restoring from time machine, etc. but I always end up back at square one looking for a permanent solution. All my drivers are the latest.
One interesting thing to note, when I had Windows 7 installed as the default startup OS with bootcamp I never experienced this problem. To me that kind of verifies that it's not a hardware problem.
My machine specs are...
      Model Name: iMac
      Model Identifier: iMac10,1
      Processor Name: Intel Core 2 Duo
      Processor Speed: 3.06 GHz
      Number Of Processors: 1
      Total Number Of Cores: 2
      L2 Cache: 3 MB
      Memory: 8 GB
      Bus Speed: 1.07 GHz
      Boot ROM Version: IM101.00CC.B00
      SMC Version (system): 1.52f9

After updating to Lion my macbook pro does not startup, it is stuck to the grey apple screen

After updating to Lion my macbook pro does not startup, it is stuck to the grey apple screen

See Here for Troubleshooting Grey Screen on Startup:
http://support.apple.com/kb/TS2570

Grey screen on startup, erratic mouse: help!

I have a new iMac 2.8 intel, after encountering many bugs getting logic 8 to run smoothly, I now find it starts just leaving a grey blank screen. I have to restart e few times before it wants to boot fully.
I managed to start it with the fireire devices on the 400 buss disconnected, tho it's started with them connected yesterday. Also the wireless mouse cursor was jumping all over the screen so had to turn it off and reset it. Can there be one cause for this behaviour?

As this the iMac G5 (PPC) forum, you would probably get a better response on the Intel iMac forums:
http://discussions.apple.com/category.jspa?categoryID=189

I have a MacBookPro1,1 running mac os x 10.6.8. It keeps freezing whenever i use it, and often takes 5 or more attempts to turn on. It just stays at the grey apple screen, causing me to force shut down. Is there anyway i can fix this?

When i am using the mac. often it will suddenly freeze, only the coloured loading wheel still moving. I will leave it for hours to unfreeze but nothing. The only remedy is to turn it off by the button. Moreover, sometimes when i turn it on it gets stuck at the grey apple screen and i have to turn it off by the button and on again. This can happen up to 10 times until it turns on! What can i do?

Shut down your computer and disconnect all peripherals (keyboard & mouse if pertinent) from your computer. Now reboot.
If the Mac starts up normally, shut it down again and then plug in one of the peripherals (keyboard or mouse first) and start up your computer again. If it does so successfully repeat the process, adding one peripheral at a time until your Mac acts up. At that point, disconnect the last peripheral you added, reboot your Mac and search the peripheral vendor's website for an updated driver.
If no driver exists or the problem remain after installing the new driver, try a different cable or a different port on your Mac.
If none of the above works, again disconnect all peripherals from your Mac, hold down the "shift" key to start up in "Safe Boot" mode.
If the Mac starts up correctly, restart without pressing the "shift" key.
If your computer still does not start up properly, shut it down and restart it while holding down the Apple+Option-P-R keys; keep holding "all 4 keys" down until you hear the startup sound "twice."
If none of the above work Disconnect all peripherals from your computer. Boot from your install disc & run Repair Disk from the utility menu. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.
Select your language.
Once on the desktop, select Utility in the menu bar.
Select Disk Utility.
Select the disk or volume in the list of disks and volumes, and then click First Aid.
Click Repair Disk.
(If Disk Utility cannot repair, you will need a stronger utility (3rd party) - Diskwarrior or Techtool PRO)
Restart your computer when done.
Repair permissions after you reach the desktop-http://docs.info.apple.com/article.html?artnum=25751 and restart your computer.
If you are able to reach your desktop take note of how large your hard drive is and how much hard drive space do you have left?
Remove any 3rd party ram.
Reinstall Snow Leopard - This will install a "fresh" copy of Snow Leopard without archiving old system files but leaves the rest of your files in place.
If your computer is still under warranty or you have Apple Care, take full advantage of it by letting tech support deal with your problems. It's what you're paying them for.
Out of warranty - take the computer to an Apple store or an AASP. Whichever is more convenient for you.

G5 wont boot past grey Apple screen and spinning cirlce

I cam in to work this morning and found my Mac on with fans blazing the the display just showing the grey Apple screen and spinning circle. I have it set to turn on before I arrive at work and it has been doing so flawlessly for all the years I've had it. When I shut down last night everything was working fine. Now this.
I've scanned some help forums but can't quite determine what the cause might be. Old battery on the memory card, a bad memory chip, ...I'm not sure.
As I said, things had been working flawlessly for years.
I've tried unplugging and re-plugging in the power cord (nope), resetting the PRAM (didn't work), Pressing the PRAM button on the memory board (again no), resetting things from Open Firmware (Using these commands: reset-nvram, set-defaults, reset-all -- no luck)and now have Disk Utility repairing permissions from the install DVD. That doesn't seem to be doing anything, it has been "Determining correct file permissions" from my startup disk for about 20 mintues now...usually it goes a lot quicker.
Any thoughts? This is my primary work machine and if I can't get it running I'm dead in the water. I'm accessing these forums from a PC in the office and would rather not have to, hahah.
Thanks.
(also, when running permission repair, do you repair the volume or the primary disk? I'm repairing the named sub-volume of the hard drive.)

(also, when running permission repair, do you repair the volume or the primary disk? I'm repairing the named sub-volume of the hard drive.)
I repair the hard drive that contains the Startup volume, unless multiple partitions are present.
In that case, only the startup volume.
Rather than "repair permissions", "Repair Disk" is what you should run on the startup volume.
Troubleshooting:
http://support.apple.com/kb/TS2570
http://support.apple.com/kb/TS1417
Reseating the RAM and graphics card may also be helpful.
If you get the machine started again, install Applejack for future help:
http://applejack.sourceforge.net/

My Macbook Pro will not load past grey Apple screen...

Last night my Macbook Pro froze so I closed it and went to bed. Today when I opened it, it was still frozen, so I held down the power button and rebooted it. It got as far as the grey Apple screen with the spinning wheel and will not load any further than that. I've rebooted a couple times since and it continues to do the same thing, stays on the grey screen forever.
I searched this problem on the Apple Support Communitites and none of suggestions (holding Shift after the startup tone, holding Command+R) have worked so far. Is there any way to fix this problem without losing my data or having to pay to talk to Apple Support? PLEASE HELP! :(

Zzoozu wrote:
None of that made sense to me or helped me. Anyone else? Maybe someone who has answers dor someone not a computer genius?
Then we can't help you as we need you to be able to help yourself and the instructions are complicated and long to paste here over and over again for the same proceedure.
Hire the services of a local Mac computer repair before you delete your data by accident.
You can jump down and do #8, that might clear the issue right away, but some programs are not going to work and require updating or reinstalling again.
..Step by Step to fix your Mac

My computer suddenly decides not to work and turns on but does not go past the grey apple screen with the loading wheel.. it will not go to my desktop. What should i do?

can somebody please help me fix this issue, i have been sitting at my computer all last night and this morning trying to figure it out. It could be the hardrive or anything really i just need to get it working. Alot of important things that need to be done using this computer and i am freaking out.
My computer suddenly decides not to work and turns on but does not go past the grey apple screen with the loading wheel.. it will not go to my desktop. What should i do?

Put your install DVD into the optical drive (CD/DVD drive) and reboot. Be sure to either use the disc that came with your Mac, or, if you installed a later Mac OS X version from disc, use the newer disc. As soon as you hear the boot chime, hold down the "c" key on your keyboard (or the Option Key until the Install Disk shows up) until the apple shows up. That will force your MacBook to boot from the install DVD in the optical drive.
Or if you are running 10.7 Lion, boot from the recovery partition (Command +R on boot) and use Disk Utility to repair your OS 10.7 partition.
When it does start up, you'll see a panel asking you to choose your language. Choose your language and press the Return key on your keyboard once. It will then present you with an Installation window. Completely ignore this window and click on Utilities in the top menu and scroll down to Disk Utility and click it. When it comes up is your Hard Drive in the list on the left?
If it is, then click on the Mac OS partition of your hard drive in the left hand list. Then select the First Aid Tab and run Repair Disk. The Repair Disk button won't be available until you've clicked on the Mac OS partition on your hard drive. If that repairs any problems run it again until the green OK appears and then run Repair Permissions. After repairing use Startup Disk from the same menu to choose your hard drive for restarting from your hard drive.
If your hard drive isn’t recognized in Disk Utility then your hard drive is probably dead.

Grey pixelated screen on startup?

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