I really don't know anything about Windows XP nor do I know how the Voodoo5 card works with XP (I have a Voodoo 5 5500 as well). You did try the WickedGL solution, right?
p.s. NatePalm - I have the same setup as you and my JO is showing me clouds and sky just fine. Don't know why you don't see it.
Beware of El Pollo Diablo!