Sounds like you need a new video card that will be able to run the game.
First check to see if you have the latest directx installed first, which is 9.0c
If it still doesnt work then you need a new video card.
download fresh diagnose and install the program.http://www.freshdevi.../downfiles.html
Then open up the program, click on hardware system then find system slots. Now goto save and save the system slots info so you can post it here in the forum and I can tell you what kind of video card you can get.
Also give me your budget on a video card. The sims2 doesnt require a real fast video card so you should be able to get one for a decent price if thats the most graphically intense game you have. Around $100 video card will get the job done and be a decent video card.