Q: After getting the dreaded gray/blue screen, I tried to run disk repair on the internal disk. I got an error message saying "Disk Utility can't repair this disk and restore your backed-up files. The volume Macintosh HD could not be verified completely

Clean Install of Snow Leopard

Be sure to make a backup first because the following procedure will erase

the drive and everything on it. See below for how to clone a drive.

     1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

         with your computer.  Insert the disc into the optical drive and restart the computer.

         After the chime press and hold down the  "C" key.  Release the key when you see

         a small spinning gear appear below the dark gray Apple logo.

     2. After the installer loads select your language and click on the Continue

         button. When the menu bar appears select Disk Utility from the Utilities menu.

         After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

         size.)  Click on the Partition tab in the DU main window.  Set the number of

         partitions to one (1) from the Partitions drop down menu, click on Options button

         and select GUID, click on OK, then set the format type to MacOS Extended

         (Journaled, if supported), then click on the Apply button.

     3. When the formatting has completed quit DU and return to the installer.  Proceed

         with the OS X installation and follow the directions included with the installer.

     4. When the installation has completed your computer will Restart into the Setup

         Assistant. Be sure you configure your initial admin account with the exact same

         username and password that you used on your old drive. After you finish Setup

         Assistant will complete the installation after which you will be running a fresh

         install of OS X.  You can now begin the update process by opening Software

         Update and installing all recommended updates to bring your installation current.

Download and install Mac OS X 10.6.8 Update Combo v1.1.

You may be able to backup your data if you have an erased external drive you can use. Before you do the above but after you have opened Disk Utility you can try to clone your drive:

Clone using Restore Option of Disk Utility

  1. Open Disk Utility.

  2. Select the destination volume from the left side list.

  3. Click on the Restore tab in the DU main window.

  4. Select the destination volume from the left side list and drag

       it to the Destination entry field.

  5. Select the source volume from the left side list and drag it to

      the Source entry field.

  6. Double-check you got it right, then click on the Restore button.

Destination means the external backup drive. Source means the internal startup drive.

Now this will only work if the drive is accessible and can be cloned by Disk Utility. Otherwise, you would need to access your drive from another Mac that you can connect via Firewire - Target Disk Mode.