Mac OS X 10.6: Partitioning a disk
Use Disk Utility to partition a disk into sections, or “partitions,” 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 to organize your information in a logical manner.
Note:To create a partition that contains Windows, use Boot Camp Assistant.
Partitioning a disk may erase 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.
To partition your disk:
Open Disk Utility, in the Utilities folder in the Applications folder.
In the list at the left, select the disk you want to format. Then click Partition.
For more information on partitioning, click the Help button (looks like a question mark).