AMD Athlon 64 X2 3800+ @ 2.2Ghz
1GB Corsair DDR-400 RAM
ASRock 939Dual-SATA2 motherboard
ATI Radeon X1900 XT 512MB
120GB Seagate Ultra ATA HDD
Creative X-Fi Platinum sound card
I play at 1680x1050 with almost everything high. The view distances for everything is at maximum with shadowing on. No AA, since you don't really need it at that resolution.
It's mostly cause of my RAM. If I upgraded, I would probably get smoother gameplay. I'm just saving money for my C2D upgrade though.