Did he install Grub as the bootloader? If so, do a search (in all forums) for "Grub and WIndows XP" and you should be able to find the answer you need. It sounds to me like his bootloader simply does not contain the Windows XP info needed to boot it. You could try some of the things listed in this thread:
But that may be a bit too much right away.
If he is using Lilo as his bootloader, then search for "Lilo and Windows XP"
Either way, the answer is already here somewhere, so don't dispair...