Core 2 Duo 2.66gz
2 GB RAM
8800 GTX
well I havn't had any problems yet but depending on your Vista settings, your OS could be using up to 1.4Gb of RAM all by itself... (I'm running 4GM ram with Vista 64 bit and vista itself uses that much if I have Aero and a few other background stuff opening)
.6GB of ram is still pretty big but if your running sims and your Virus Scanner starts up I can see where you could run out of memory real fast.