Didnt we establish you had the Intel Integrated jobby in your Sims2 thread? Or did you upgrade since then??
I had trouble with GTA3 too on a 9800 Pro. I think the game is just old and hasnt been updated to run with newer drivers...sucks I know! On the other hand GTA:San Andreas kicks ass! :P (altho it still has a few crash to desktop issues atm...)