xp use a nt backup.
but maybe you can try to plug the win98 backup in your xp os & run it from xp os. maybe some dll will be required. in that case, to pick them from 98 os & put them in the xp os could be sufficient.
its just a little trick to restore your backup if it is an important one.
i have already did this kind of things when i have switched from 98 to xp.
<i>if <b>you know</b> <font color=white>you don't know<font color=black>, the way could be more easy ...