Abnormally low performance

[Martal]

The main specs :

ATI 3870 (not sure about memory)
2 GB DDR2
AMD X3 8450 (the 2.1 Ghz one)
A somewhat random 500W PSU
Windows 7

You might say that this is already an ancient system and I'd agree but the thing is, I'm playing games on a 17 inch monitor and the things im trying to play aren't exactly the latest releases (Bioshock, Crysis Warhead, Burnout Paradise). On all those games, I start to lose frames rapidly when approaching anything near high settings. And this is on 1024 x 720. Any ideas what could be causing this?

[chequers]

You mean the game slows down after a few minutes of playing? Overheating. Watch the CPU and GPU temps.

If you just mean a touchy feely "I think this system should be faster", grab 3dmark, benchmark it and compare to what others with similar systems are getting before investigating any further. I'll bet dollars to donuts your performance is average.

[Hugin]

The main specs :

ATI 3870 (not sure about memory)
2 GB DDR2
AMD X3 8450 (the 2.1 Ghz one)
A somewhat random 500W PSU
Windows 7

You might say that this is already an ancient system and I'd agree but the thing is, I'm playing games on a 17 inch monitor and the things im trying to play aren't exactly the latest releases (Bioshock, Crysis Warhead, Burnout Paradise). On all those games, I start to lose frames rapidly when approaching anything near high settings. And this is on 1024 x 720. Any ideas what could be causing this?

Can you define what framerates you're getting? Crysis Warhead is not going to run very well at anything near high settings on a HD 3870 and 2 gigs of memory.