it could be the ram but i doubt it. most games don't need 2gb to max out the games.
what kind of settings are you using and what FPS are you getting?
also you could try turning down the anti-aliasing if it's a problem. i never put mine up past 4x because i feel it's fruitless
Antec NeoPower 650W
Intel Core 2 Duo E8400 (w/ Arctic Freezer 7)
4GB DDR2-1000 G.Skill
Sapphire x1950 Pro 512mb (w/ V700)
250GB, 500GB and 1.5TB Seagate Barracudas (2.25TB total)
Fatal1ty XtremeGamer sound card *** generic TV tuner
Xclio 3060 case *** HannsG 22" monitor
XP Pro / Ubuntu 7.10 *** Razer Copperhead and Tarantula