Ok your running a Nvidia card now so you will want to stay with Nvidia. So everything ATI ! throw out the window. IMO Nvidia is much better anyways. The new budget cards out now days will flat out scream if you buy the right one. i need to know more about your machine though.

go to start, Control panel click System: Tell me what Processor you have. It should say AMD or Intel and a Speed. ie 2.6 or 3.0 GHZ. Then i need to know what RAM you have. 1 gig or 2 gigs ect.

See the key is to match your components it saves time and money in the long run. Some people put a 75 dollar card in a 2000 dollar computer and they wonder where they went wrong at. lol

I built my last PC and put the best stuff in it that was available at the time. Then moved to the country and can't even get internet lol. STILL ! But i went balls out on a GFX card and even with a 1000 dollar processer Intel Xtreme quad core 3.2 it couldnt push the Gtx 295s i had. So.... I had to over clock from 3.2 up to 4.6 speed to get it to run all together. Look at a computer like a football team if you will, When one part struggles, They all struggle ! till the fatal crash and burn.

ok enough rambling... get back to me with info dotty.