A big part of the problem with 64 bit is the drivers need to be completely re-written. In addition to this, for Vista 64 bit, you need to have the software certified and "signed" by Microsoft in order for it to work. You know all those drivers that work under XP(32 bit), but you need to give specific permission before installing? That won't work under 64 bit Vista, so it has to be fully checked by Microsoft before it will work.
Hm.. So it doesn't. Bizarrely enough, apparently all the games I've been playing since I got this were ones that never worked under GJ (Blizzard games) or didn't need the CD.
I didn't realize the Far Cry 64 Bit edition didn't do a CD check, and other games I've been launching don't. Heh.. Wow. Now I feel like an ass.