I was recently running Windows XP x64 to take advantage of the 64-bit Athlon processor in my machine.  But of course there were problems.  I was unable to listen to sounds that needed software rendering due to driver issues.  Another problem was that with iTunes and my iPod software, I had to mess around and enable a few settings before it would allow me to add songs to my iPods.  This was getting quite annoying and since I had free time, I’m back online with 32-bit Windows.  For anyone with a 64-bit processor, I would wait to get an OS that is better updated, such as waiting for Vista when it comes out, or going with a non-Windows OS.  I am sticking with XP until Vista comes out and is stable, because I do not feel like messing around with Betas or OS’s that are extremely vulnerable.  But I am looking forward to the improvements that are in the new Windows OS.