How to install new VGA ?

im trying to install a new VGA because it says my old one is unknown. But when i used a program to check what it was it said this ATI Technologies Inc Mobility Radeon 9100 IGP (RS300M AGP). so i tried installing that one and it wont work. I need to install a new VGA so its compatible with directx 9.0 so i can play the sims 2. plz help.