tip for anyone who cares (I've just learnt this the hard way):
If you have a 3dfx / Voodoo based video card and want to upgrade to XP... don't.
Since 3dfx went out of business last christmas (did you know their software engineers were based in Belfast?!) there's been ZERO driver development for XP.
You can still use it to do basic Windows stuff, but forget about any form of acceleration for graphics apps or games. nVidia shall soon rule the Universe, it seems.
...and directX shall be their Grand Vizier