I actually posted about this a while ago. If you want to use x64 make sure you have spare time. It is better than SP2 simply because one it has the same capabilities already built in, and it can utilize the full potential of a 64 bit processor. There are some problems with it (that's why it is a beta), also you have to find the 64 bit versions of the drivers you will need for your hardware. If your hardware like video card are no longer supported by the manufacturer then you are out of luck and you should keep x86 windows. Also, i would take a spare hard drive or buy a 40 gig hard drive or smaller, you know something cheap. And install x64 on that and use it as a test bed, after a few months if you are happy and if you were able to solve any major problems you should keep it. Also, microsoft is saying that when they finally release 64 bit windows to the public they will give free upgrades from 32 to 64 bit, if your processor supports it.