When to upgrade and where to start
I built an XP PC about 2 years ago and just had one of the nVidia 7200 series cards die. The mobo has PCIe x 16 and most of the newer cards are PCI 2.0+ so my question is should i just replace the GPU or start rebuilding completely.
An HD5770 should work well for you. It's quite good though not great at that resolution and costs $150-160;
Your CPU is a bit on the weak side for current games but it should still be mostly capable. It will likely limit the card a bit on the more CPU intensive games but it's no big deal for a light gamer. FYI your motherboard can still handle pretty much all current AMD processors should you want an upgrade. A quad core Athlon II is only $100 but even a $60 dual core would be a nice upgrade.
The HD5770 may be able to work on your current power supply. Tell us the brand and model.
Power supply was stock that came in the Eagletech Dragon case. Not sure of brand/model untill I can pull case apart when I get home from work. oh and clarified in system spec that it is infact a dual core but will be hitting new egg to look for an acceptable AMD up-grade.
@ jyjjy - what resolution is it good at and are crossfire cards compatable with an SLI MOBO?
Nah, the Phenom/Athlon II chips are a significantly better architecture than the original Phenoms.
As for resolution like I said before the HD5770 should be quite good for 1920x1080. You won't be able to max out every current game at that resolution but you will be able to on most and on most of the others you'll probably just need to turn AA off or down. Not a big deal at such a high resolution imo.
If you are asking if it is compatible with your motherboard the answer is yes. If you are asking if you will be able to use two in crossfire at some point the answer is no. Your board is SLI and you would need Nvidia cards to use two at once. Unfortunately Nvidia doesn't really have any competition in the price range you are looking at right now. There is only the GTX 260. It performs similarly to the HD5770 but it both costs more,and is older tech that is significantly less power efficient and isn't DX11 compatible. Nvidia is actually supposed to release the GTX 460 sometime this month for about $200. You could wait and see how well it does in benchmarks and if it is a worthwhile choice for the money compared to the HD5770 if you aren't in a rush.