Reinstalling the Software That Came with Your MacBook
Use the software installation discs that came with your computer to reinstall Mac OS X
and any applications that came with your computer. You can choose “Archive and
Install,” which saves your existing files and settings, or “Erase and Install,” which erases
all your data.
Apple recommends that you back up the data on your hard disk before
restoring software. Because the “Erase and Install” option erases your hard disk, you
should back up your essential files before installing Mac OS X and other applications.
Apple is not responsible for any lost data.