The format of the partition table is an annoying hangover from the original IBM PC. It's a classic example of 'I wouldn't start from here' - why on earth do you have to still care about heads and cylinders? Especially as the actual disk drives re-re-re-translate the figures that various other bits of code have already translated back and forth, just in case you have ancient kit, and not always got the answer right.
So I've used this as excuse to put in a new hard drive and install WinXP Pro on it, dual booting along with Ubuntu.
For some curious reason, XP has decided that its partition, the only one it can see, should be... G:\
Erm, why?!? I'm slightly reluctant to reinstall it (although I've not done much with it) because that either means reinstalling Ubuntu (which has had more done in it) or faffing around with tools I no longer trust as much as I once did...