Well, I believe it's around 3+ years since I had 1GB in my XP32 machine, and things might have gotten a bit heavier since then. But 3 years ago I gamed (a lot) more than I do now, and I still used Visual Studio - so you're probably running some relatively intensive stuff if 1GB isn't enough

- 2GB should be a pretty sweet spot, though (and indeed, with the RAM prices of today, less doesn't make much sense).
My current system runs XP64 - for client versions of windows, there isn't really any way to utilize more than those ~3.5GB (real value depending on BIOS, chipset and installed hardware). Or, well, you could load a pre-SP1 XP since that imposed a limit of 4GB
physical memory, rather than the
address space limitation that SP1 changed to. Some drivers might have problems with this, though (and, on a related note, some driver developers should be shot or at least moved to userland). If you want >4GB memory on a 32bit Windows OS, you really have to move to server versions, which don't have this artificial limit imposed.
If you're going to jump gun and run a 64bit OS, I'd say go for Vista. It really isn't a bad OS once run through
vLite. On the other hand, it probably makes more sense just to run XP32 for now, and going 64bit Win7 once that hits the streets
