Call Of Duty:World At War help please?

I just bought and installed the game and patch. When I'm playing single player, it doesn't seem to be able to handle my resolution, which is 1920 x 1200. I run COD4 perfectly on this, and even with low detail this feels jerky/chuggy, like slow motion. Also, when I try to do things in options sometimes it gets stuck and freezes. I feel that some of this game was done very half-a$$. Multiplayer was alittle bit more tolerable, although I had to run it on low settings. I don't understand why it's running so poorly on a new computer. I have a vista with a Nivida card that is supposed to play new games. Help is appreciated. Thanks!