Not sure what you mean. You can just put the XP cd in the drive and reboot. I would make an empty drive/partition ahead of time though. After you do this, you'll need to boot with your linux CD and fix the master boot record to be able to boot linux. Or if you're installing from scratch, install Windows first (leave the blank partition at the end for linux) and then install linux 2nd. It'll find your windows install. If you dual boot like this, be sure to create a FAT32 partition to share files (like word docs, music files, photos, etc) that you want access to when you're in either linux or windows.
Or you can try installing VMWare server and install a virtual machine of XP. I haven't done it, but a guy at work did. Note that you need extra RAM to do this because you have to dedicate some amount to the virtual machine (probably 512MB would work for XP).