Your computer is quite old as you noted and nothing is going to make it sufficient for current games. If you would like something that will help you play games that are a few years old then you have an AGP slot. Look for a used AGP 6800 GT or 7600 GT/GS perhaps.
No its not for games thats what the xbox is for lo. lm just looking for a graphic card that i would be able to run windows areo and stuff like google earth.