Help need on Repairing Snow Leopard Version 10.6.6

Question

I believe that some of us have seen this stuff at one time or another on Mac OS X. I'm running (version 10.6.6)
Verifying volume “Macintosh HD”
Performing live verification.
Checking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Checking multi-linked files.
Checking catalog hierarchy.
Invalid directory item count
(It should be 43 instead of 42)
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
The volume Macintosh HD was found corrupt and needs to be repaired.
Error: This disk needs to be repaired. Start up your computer with another disk (such as your Mac OS X installation disc), and then use Disk Utility to repair this disk.
and I'm wondeinfr on the best way of repairing it since Mac OSX keeps unmounting my backup drive when I try to preform a backup using Time Machine.
Another question that you might help me out on is which installation disc should I use if I try to repair the OS. The Leopard disc or the Snow Leopard disc and what is the key you hold down and for how long.

Answer 1

Time to try fsck (Print out or write down these instructions since in single user you won't have the page open when doing this.) You must enter the commands exactly as written, observing spaces and case.
*+Use fsck if necessary+*
+fsck is a command-line utility that may be able to verify and repair a disk. If you can successfully start up in Safe Mode or use Disk Utility while started up from a disc, you don't need to use fsck. Here are some situations in which fsck may be necessary.+
+* Your Mac OS X disc isn't available.+
+* Your optical drive isn't available.+
+* You can't start with a Safe Boot by holding the Shift key during start up.+
+Tip: If you use a Mac OS X Extended (Journaled) formatted volume, such as with Mac OS X 10.3 or later, you probably won't need to use fsck. If you do use it for any reason, please be aware that benign error messages can appear.+
+If you're not sure how your volume is formatted and you can't start up from your Mac OS X volume to find out, type the following command in a command-line interface and then press Return: diskutil info /+
+If you see "File System: Journaled HFS+" returned, you have a Journaled volume.+
+To use fsck, you must run it from the command line. Unlike using your mouse pointer to open an application to do something, you'll need to type a text command at the prompt (#) to tell fsck what to do. The Terminal application (/Applications/Utilities) and single-user mode are two examples of command-line interfaces in which you can type such commands. To use fsck:+
+1. Start up your computer in single-user mode to reach the command line.+
+Note: If necessary, perform a forced restart as described in the Emergency Troubleshooting Handbook that came with your computer. On desktop computers, you can do this by pressing the reset/interrupt button (if there is one) or holding down the power button for several seconds. On portable computers, simultaneously press the Command-Control-power keys. If your portable computer doesn't restart with this method, you may need to reset the Power Manager.+
+2. At the command-line prompt type:+
+/sbin/fsck -fy+
+3. Press Return. fsck will go through five "phases" and then return information about your disk's use and fragmentation. Once it finishes, it'll display this message if no issue is found:+
+** The volume (nameofvolume) appears to be OK+
+If fsck found issues and has altered, repaired, or fixed anything, it will display this message:+
+*** FILE SYSTEM WAS MODIFIED ***+
+Important: If this message appears, repeat the fsck command you typed in step 2 until fsck tells you that your volume appears to be OK (first-pass repairs may uncover additional issues, so this is a normal thing to do).+
+4. When fsck reports that your volume is OK, type reboot at the prompt and then press Return.+
+Your computer should start up normally and allow you to log in.+