My friend has the average of 35-40 fps on his old 1024x768 LCD with an HD 7750 on Crysis (Very High sets, 4x AA). You could get 50 with the CCC Optimization pack.
Skyrim and others are not such demanding titles but Battlefield BC2 should also require at least the 7750.
This card is not expensive these days, does not require an external power connector like the 4850 does, performs better, and has a greatly optimized DX11 support. Save up for a few weeks or months, but DO NOT go any lower than that.
my craphic card hasnt make any of those issues since i reinstalled whole machine using win 7 and now it works like a charm. maybe something wrong with dx9 base or something went wrong with software. thanks for your help ppl.