Mac OS X 10.5 Help
Partitioning a hard disk
Use Disk Utility to partition a disk into sections, or “volumes,” each of which works like a separate disk. You might want to partition a disk so that you can have different versions of the Mac OS, or organize your information in a logical manner.
Partitioning a disk erases all the files on the disk. If you have any files on the disk you want to save, make sure you copy them to another disk before you partition the disk.
You cannot partition the disk that you started up from. If you want to partition the startup disk, you must restart your computer using your Mac OS X Install disc, as described below. Because partitioning will erase your hard drive, you should back up your hard disk before proceeding.
To learn more about using Disk Utility, open Disk Utility, in the Utilities folder of the Applications folder, and choose Help > Disk Utility Help.
To partition your startup disk:
Insert the Mac OS X Install disc and restart the computer.
When you hear the startup tone, hold down the C key until you see the progress indicator (looks like a spinning gear).
When the Installer appears, choose Utilities > Disk Utility.
Select your disk from the list, and click Partition.
Select how you want to partition the disk and any options you want, and then click the Partition button at the bottom of the window.
Quit Disk Utility.
When the Installer opens again, you can install Mac OS X on one of the partitions.
If you want to use another disk as the startup disk, choose Utilities > Startup Disk and choose it.