Building a new machine in August. I'm gonna need to sort out some kind of second machine in the summer, figured I'd take the opportunity to treat myself, plus my current machine is getting on a bit. Just some issues - It'll likely be an AM2-based AthlonX2 CPU. With that in mind, I was going to look at XP 64-bit. Is there any actual disadvantage, or problems that come with using 64-bit Windows?