I also have a P5KE, something like that mobo and I'm running Vista Ultimate 64 with it no problems.  I have 8 Gig RAM in there also, my proc is a Q6600. My graphics card is similar, an 8600 GT

I always use the Poser Shader Tree on my imports into Vue6Inf and with this system have not encountered any issues with OOM messages, I have one issue which remains unresolved and not sure what is causing it, and that is my Mouse over tool tips don't work, no biggie though, can always get what I don't know from the manual!!

If you don't want Vista, I believe you can still get XP64 but I find Vista ok and they send improvements nearly every day [LOL].

Injustice will be avenged.
Cofiwch Dryweryn.