"Thor, I would recomend using Win Xp Pro 32bit...It will be hard to get support for the 64bit version at this point. And in reality there is really no point in running the 64bit version when there are so few program that can utilize it."
I actually run Win x64 on three different computers and the it can run every program I've tried. It doesn't have any problem running programs, the problem is driver support for hardware. You have to find the x64 drivers for everything as it won't recognize any 32-bit drivers, which can be a pain. In the end the only, ONLY thing that haven't been able to run on Win x64 is my HP laserjet 1012, and I hear there is a workaround for it but I just preferred official drivers so there are no surprises.