Were you experiencing a problem with vista that made you want to downgrade? With 4 gigs you will be able to run vista full graphics with no problem. 90% of program and driver compatibility issues were fixed with SP1. I agree, xp 64 bit is worse than vista. On top of that, vista has a very nice solution to 32 bit emulation for programs that are not compatible with an x64 architecture. I seem to remember XP being quite a catastrophe when it was released, SP1 made it much more stable, but too many people clung to windows 98 and 2000 (or
*cough* Millennium Edition). Retrospect is always 20/20.
While xp 32 might be more "stable", you are missing out on several key features that Vista offers. The two biggest of these are:
Varying support for near 4G of ram and absolutely no support for > 4G (as was stated previously).
The other big thing people forget about is DirectX 10. If you're going to be gaming at all, you're missing out on quite a bit by sticking with XP, since it only supports up to DX9.