|"her Xp computer is all screwed up"|
Defined "screwed up". It *may* be an easy fix.
Doing a format/reinstall is pretty drastic. She will lose EVERYTHING - docs, pictures, programs, etc - unless she has them backed up. You will need the XP Product Key, plus ALL the hardware drivers (chipset, video, sound, network, etc). These drivers will most likely NOT be on the XP disc. Depending on which disc she has, SP3 may have to be installed, not to mention IE8 & all the other numerous Windows Updates. Then of course, there's the programs - antivirus, firewall, MS Office (or similar), plus whatever else she uses. This will take several hours. Are both of you prepared for that?
Use the following to find the XP key, but you have to run it from within Windows. Is her system still bootable?