Weird. There are people here that know more about this than me, but it sounds like you may have gotten a defective disk. With specs like that and the latest drivers, you shouldn't be having any problems. I'm running it on an AMD 64 with the same graphics card and memory, and it's running smoothly.
When you get it taken care of, PM me and we can get a game going
edit: did you try to re-install it?