Need Advice Re: Upgrading My Crappy Computer

[Galactoman]

H'Okay. Any of you who've run missions with me know that my computer is crappy. It takes me a very long time to load missions, and there are certain zones that cause me to lag more and more the longer I stay in them (I'm looking in your direction, Faultline!). I'm running Verizon (now Fairpoint) DSL, which runs pretty fast and has run the game fine when friends with better computers have plugged into it. I bought the computer at Sam's Club about four years ago, and even with my "economic stimulus" Bush-money I still can't afford to buy a better one. I can, however, afford to buy some stuff FOR it.

My computer is a Compaq Presario SR1115CL, a model that seems fairly obscure as newegg.com doesn't even list it as existing.

I just the other day ordered more RAM to boost my computer to its maximum RAM of 1 gig (lol) which should help a bit (hopefully).

However, my graphics card needs to go. It's a Nvidia GeForce FX 5500, a clunky monster with a fan the size of a fist sticking out of it (which sounds like a vacuum cleaner, or at least it did until it stopped working a few months ago). As far as gaming goes, I pretty much only play CoH on this PC. I'm not concerned with running top-of-the-line games, but I'd like to be able to run a game from four years ago WELL. Graphics cards are a bit of a mystery to me, and I'm always terrified of spending a ton of money on one that my computer won't recognize in the first place.

Can you guys offer up some suggestions or advice? What are good brands and models of video card that will work with my computer? Will I need a power source for them? Is there anything else (besides noob stuff like running virus-scans and defragmenting and stuff) that I can do to speed up my performance?

Thanks in advance,
HFB/GalactoDan