I've been madly downloading the Vista 32bit and 64bit versions from the MSDN site. I run an AMD 64bit CPU at home, so I downloaded that first... but it seems like the 32bit version of Vista is still the way to go.

From:
http://blogs.msdn.com/tims/archive/2006/05/28/609372.aspx
http://www.winsupersite.com/showcase/winvista_ff_x64.asp

The 64bit version requires that hardware drivers be signed, with no ability to accept unsigned drivers. Which means you need to look at the hardware compatiblity list before purchasing anything. Great for a high-end scientific workstation, but too much hassle for a home computer.

One neat tibit is that you get both the 32bit and 64bit versions when you buy the Visat. Each on its own DVD, then are licenced to use one at a time. So at least you can try the 64bit then go back to 32 if need be.

Wish I would have read this before choosing the order of these 8 hour downloads...