20" intel iMac is having bad week, "Sleep" hiccup, now can't find system

Question

Hi all,
I'm running a 20" intel iMac, purchased new in January 2008. It's been a trooper.
A handful of days ago, it developed an odd glitch. The fan would "power down" like what one hears when the computer would go to sleep -- but this would be in the middle of use. It would immediately come back up. No screen dimming. On most occasions, this would take down open and in-use programs (for example, Safari).
Today it again did this, and shortly thereafter, the system "froze" (cursor was movable but no reaction from any open program; no visible activity from anything running). I rebooted by holding the power key for 10 seconds, waited for some time (±15 minutes), then came back to power it on. It powers up, fan spins up, white screen with apple and the spinning wait icon (not the beachball, but the "clock lines" one normally sees at restart). It does not progress beyond this point.
In short, I see this as two troubles that I need help with.
1. The system was damaged/corrupted during the last startup, and the drive can no longer see it.
2. There is a problem with the fan, a possible overheating issue, or perhaps an issue with a power module/SMC. The fact that programs are crashing with this makes me somewhat skeptical of this being merely "dusty fan" or even common overheating.
I'd like an idea of what steps to take next, either to diagnose what is wrong with my iMac, or to bring her back to health.
Message was edited by: gwenners

Answer 1

HI,
Unfortunately, it sounds like the startup disk needs replacing.
Boot from your Mac install disk and run Disk Utility.
Insert your install disk and Restart, holding down the "C" key until grey Apple appears.
Go to Installer menu and launch Disk Utility.
Select your HDD (manufacturer ID) in the left panel.
Select First Aid in the Main panel.
*(Check S.M.A.R.T Status of HDD at the bottom of right panel. It should say: Verified)*
Click Repair Disk on the bottom right.
If DU reports disk does not need repairs quit DU and restart.
If DU reports errors Repair again and again until DU reports disk is repaired.
When you are finished with DU, from the Menu Bar, select Utilities/Startup Manager.
Select your start up disk and click Restart
While you have the Disk Utility window open, look at the bottom of the window. Where you see Capacity and Available. *Make sure there is always 10% to 15% free disk space*
If you cannot boot from your install disc, try booting in Safe Mode
What is Safe Mode
If the hard disk appears to be ok, you could try Resetting the SMC
Carolyn