Boot from the windows 98 cd (don't launch the win98 setup) and get to a command prompt with cd support. cd to \win98 and type in fdisk. Delete the xp partition and create a new primary partition. Reboot the machine when told to and boot from the win98 cd again. Go to the prompt with cd rom support and cd to win98 again and then type format c:. It will ask you if you are sure, just chose 'y'. After this is done boot from the win98 cd one more time, but this time run setup. This should get you going. If you get into any problems, just let me know. (I think I got all the steps in there. I wrote this from memory.)