Disk Utility Download
You do not have to boot up with an external drive. Start up from OS X Recovery. For such, you can just press Command R while starting up your Mac.
I have a mac book pro software was updated to 10.6.8 and they added 1 meg ram. I now have red in the backround and all pictures i photo.black and white wall paper has red in clouds and backround. Using Disk Utility to verify or repair disks Learn about using Disk Utility to verify or repair disks. Disk Utility can verify your computer's startup disk (volume) without starting up from another volume. My old mac running on snow leopard 10.6.8 had some files that i needed. I couldn’t remember the password to my main or admin account, so I tried resetting the password to the main account. I got to step 8, and after that, the first time I wrote sudo reboot. Feb 08, 2012 While this is still the case while booted in most versions of Mac OS X, you can repair the Mac OS X boot disk thanks to Mac OS Recovery Partition, preventing the need from using an external boot drive to repair the disk. The trick is to boot the Mac into Recovery Mode first, and run the Repair function from there. Lets try this repair Open your finder ( magnifying glass ) type in disk utility, and launch the disk utility application. On the left side of the disk utility window, click your mac hd, then at the lower right hand side, click repair permissions. 
Keep holding on until you see the circle that begins to load OS X Recovery. Let go your hold and wait till Mac OS X Utilities begin. 
Best book reader for mac. Click on Disk Utility.
Select the drive partition where OS X has been installed. Click on Unlock and provide password because your disk is protected by Vault. Now, you are ready to Verify Disk, Repair Disk, Verify Disk Permissions and also Repair Disk Permissions. You would like to do one at a time. Once alls done.
Quit Disk Utility, quit Mac OS X Utilities, and hit Restart. You will be good my friend. Which drive do you think you have FileVault enabled? Highlight the partition of that drive.
Once you highlight it (click on it), check the MENU on top. One of them (probably 3rd option) would be Unlock or similar. Also make sure your mounted OS X partition is grayed out. Grayed out means locked because of FileVault. When it's grayed out, it would not allow to do anything disk related.
You must unlock or say decrypt it. If you see DECRYPT in the menu, you can do that as well. If you do not see menu, you can click on View from finder and then show Menu items. Hope it helps.