Actually kraz, i'm running 1.3 ghz 386 ram, and GeForce 4 Ti4400 and have no problems with the game at all. My brothers computer with lower specs has no problems with the game either, it just doesn't look as nice as it does on mine because i have the nicer vid card.
I'd reccomend Halo of course, its a sweet FPS game that very replayable and the multiplayer is quite fun!
If you want an all around War game check out World War 2 Online(its MMORPG so monthly fee) its basicly a half scale model of europe on a constant map and you fight out WW2...you can be infantry (fps) tanks planes Anti tank guns etc...very very fun doesn't get old fast like some other games might.
www.wwiionline.com