Disk Utility is the program included in the OS X operating system that allows you to perform repairs and first aid on disks connected to a computer. However, disk utility cannot repair the disk on which it is located. To repair the startup disk of the computer, you must boot up into Disk Utility using the Mac OS X Install DVD that came with the computer.
Insert the Install DVD in the computer.
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Click the power button on the computer and press "Restart." Press the "C" key on the keyboard right away and keep it held down.
When the language selection window opens, release the key and select your language.
Open the "Utilities" menu and select "Disk Utility." If you are using OS X 10.3 or earlier, open the "Installer" menu and select "Open Disk Utility." Disk Utility opens and you can repair any hard disk attached to the computer.