Athlon XP 2600+ (1.966 GhZ)
ASRock K7S8XE Rev. 3
1 GB DDR-RAM PC333 (not 100% sure 100% sure about its frequency now)
PNY GeForce 7600 GS / 256 MB DDR2-RAM (AGP)
running WnXP SP2
its probably - maybe except for the processor the maximum of what you can and should do upgrade with a good old AGP system. Seeing that there are hardly any new AGP cards coming out, facing the fact that the maximum processor speed that I could upgrade with my system isnt really far above the currently installed one, the next step is buying a new system with a PCI-E enabled motherboard sooner or later. So far, this machine is a good plattform for newer games that are not stuffed with highend gfx and effects, and even titles that are more hungry for hardware can mostly be played on medium settings.
On topic: your settings are quite fine. Concerning the gfx card, you might use Everest Home Edition or simply the ATI Control Center or Device manager to check what model it exactly is, the X... cards differ greatly in performance. A 512 mb built-in card would be rather uncommon, although its not impossible, since it might not have true 512 MB of RAM, but uses up to 512 mb of your 2 GB system ram (the shared memory stuff is often masked with terms like "HyperMemory" or "TurboCache"). Besides that, your pc should suit most games for at least 2 years.
