You can use a program called Partition Magic. You can use it to create any kind of partition you'd like, and create a dual boot drive. Beware, you need version 8.0 or higher to work properly with WinXP. You can create this partition without wiping the master boot record, and you theoretically won't loose your data. I use it all the time, but beware of the ver 8.0 thing with XP, or you will certainly lose everything. It's far easier than using FDISK.
Greg