You should be able to reformat by booting from the cd.
Make sure you only choose format, and don't attempt to reinstal until formatting is finished.
It should not matter then what versions are on the disk.
Failing that, make up a floppy, with necessary programs,even an old floppy made to install windows 98 will do.
including format, and boot from that.
if you do that, you can only format in fat32, but you can change it when you install windows xp