tbh, you'll get 3.5gb, the extra 512mb dont worry about it.
32bit XP is more stable, 64bit XP wasnt a hit.
Vista 64bit and windows 7 (unified 32-64bit apps?) are a better bet.
as said by popo, drivers are always a pain in the bum.
_________________
Canon EOS 5DmkII + BG-E6 + Canon EOS 40D + BG-E2N + Canon EOS 33
Canon 17-40
F/4L USM + Canon 24-70
F/2.8L USM + Canon 28mm F/1.8 USM + Canon 70-200
F/2.8L USM IS + Canon 85mm F/1.8 USM
Canon Speedlite 580EX II + Canon Speedlite 540EZ + 2 x Nikon SB-80DX
Cactus V2s Wireless Trigger -
5 x Cactus V2s Wireless Reciever
MY FLICKR!