I'm using 32-bit windows 7. I use the pc mainly for gaming. GTA4, CS:S, divinity II, COD6, Assassins Creed, Red Alert 3, etc. As for the 5850, I'm waiting till nVidia releases the upcoming GPU's to grab one. And also, about the ram, if I buy another 3 gigs of ram, wouldn't mixing new ram and old...