Problems with DX Slimline.

I installed the slimline today. I have no problems up until actually entering the game, at which time the following occurs:
*the textures are screwed up, particularly on the walls and on the floors. The will appear striped or staticy...occasionally a row of faces will appear (I am assuming a texture glitch pulling from the face texture maps)
*smoke from shots and explosions appears blocky and staticy (I don't think static-y is a word, but you catch my drift)
* (and the worst problem) in game play, everytime I near 1 or more people, the game will become VERY jerky for a few seconds, then speed up really fast, then become jerky again...etc etc.
I don't know if the problem is with the slimline edition or with my computer. I am assuming it's my computer, which has a 128 mb graphics card, AMD Athlon 64 3200+ and 512 ram...
any ideas on what is wrong? I simply can't play DX like this....
*the textures are screwed up, particularly on the walls and on the floors. The will appear striped or staticy...occasionally a row of faces will appear (I am assuming a texture glitch pulling from the face texture maps)
*smoke from shots and explosions appears blocky and staticy (I don't think static-y is a word, but you catch my drift)
* (and the worst problem) in game play, everytime I near 1 or more people, the game will become VERY jerky for a few seconds, then speed up really fast, then become jerky again...etc etc.
I don't know if the problem is with the slimline edition or with my computer. I am assuming it's my computer, which has a 128 mb graphics card, AMD Athlon 64 3200+ and 512 ram...
any ideas on what is wrong? I simply can't play DX like this....