#1 You can test and repair disk permissions on your startup disk without starting up from another disk.
#2 You must start up from another disk, such as your Install Mac OS X disc and use Disk Utility to test and repair it.
Starting with #1 to repair your startup disk:
- Open Disk Utility, in the Utilities folder in the Applications folder. (I actually keep a shortcut for this on my dock)
- Select your disk, and click First Aid.
- Click Verify Disk.
- If the disk needs repairs, do one of the following:
Suggestion #2: If you have your Mac OS X installation disc
insert the disc and restart your computer holding down the Option key, then select the Install Mac OS X disc and click the arrow.
Open Disk Utility.
In the Mac OS X Installer, choose Utilities > Open Disk Utility.
- Select the startup disk you want to repair in the list of disks and volumes, then click First Aid.
- Click the button to verify or repair the disk or disk permissions.
If you don't have the install disc on hand... or at all... you can always try the following:
Restart your computer while holding down the Shift key. As your computer starts up, it performs a disk check similar to the one Disk Utility performs.
Use mac support to search for your answers. Here's where I found mine
