My cousin had the same problem, only way out was to install windows 95 from diskettes(not CD) then update to windows98. We left it like that as everything worked. Didn't take any chanses in putting XP, althought XP seems to be made for brand names.
I feel your pain man as it took us a who lot a couple sleepless nights and no sunlight days.
hope it helps.

PS, Celeron cpu is what I have, but in a clone box.
ok, back to cars now..