The easiest way is to re-install everything from another mac.
Or you can try this if you only have one mac:
- Insert your OSX DVD. Start the installer and let your mac restart.
- In the Installation, there's a Apple menu bar like the actual installed OSX, click on the Utilities --> Disk Utility.
- In Disk Utility select your HDD (not the volume but the main HDD). Click on the Partition, click on Options..., makesure you select the first option "GUID partition". Click OK, change the partition to single, click partition.
- After the formating complete, restart and proceed to OSX installation as you should.

This post has been edited by wei: Jul 10 2007, 02:50 PM