To answer Tom Darts question, I would say don't bother - there is less driver support etc for win64 platform and all your current software would have to be updated to 64bit versions too if you want to see a change in performance. 

Stability in 64bit windows is ok now, I use 64bit XP and 64bit server 2003 at work alongside 32bit, but I really can't see any reason to change unless you have a specific 64bit app you want to use.

Windoze really hasn't cracked into 64bit properly yet, and I have a feeling it won't for a while until microsoft get drivers sorted and push companies harder to provide 32 to 64 bit upgrade paths that are realistically priced.

----------

Toolset: Blender, GIMP, Indigo Render, LuxRender, TopMod, Knotplot, Ivy Gen, Plant Studio.