It can be done, but it's not easy, and it's risky to the files on your HDD. I wouldn't recommend anyone who hasn't backed up their stuff to give it a go. If you have, then try using Partition Magic 8 to resize your drive. Once you've installed Win98, you'll need to reapply the MBR in XP and set up a boot menu by editing C:\boot.ini on the XP partition to allow you to choose between the OSes.