In order for games to look good and run good, you also have to take into account how fast your CPU is and how much RAM you have. What do you have for a video card now? Do you know your computer specs? I play Battlefeild 2 as well. I have a Althon 2400 CPU (runs at 2 Ghz), 1.5 GB RAM, and a Nvidia 256 MB Gforce 6800 GT video card. BF2 runs ok, But I'm bottlenecked becuase the CPU is so low. BF2 is a very demanding game, they also don't have all the bugs worked out of it yet. In a couple of weeks I'm going to do a major upgrade to my system, getting a better motherboards, CPU and faster RAM so I can play the games they way they should be.
You also have to know what kind of connector your video card has for fitting in your motherboard. AGP was the norm, but just this last year they came out with a newer one called PCI express. Video cards have only one type of connector. You need to get the same one that goes with your motherboard.
I hope I'm not overwelming you. It sounds more complex then it is, really.