Well i dont play many games on the pc and i've had these games for ever i mostly play HAlf Life 2, CS:S , Arma 2, and TEam Fortress 2.
I have a BFG GTX 260 OC Maxcore clocked at 640/1105/1405
on Half life 2 FPS dip to low 20's and average at about 26.. i have Vsync Forced OFF on newest drivers.
Team Fortress 2 is the same its always on 24 fps avg...
Arma 2 is the same...
even on CS:S i never go beyond 33 Avg...
The highest ive seen it go was 56
Anyways i use a 26 inch TV at the resolution of 1280x760 could that by why?
My specs are
asus m2n68 am se2
Amd phenom 8750x3 @ 3.10 Ghz
3 GB DDR2 800mhz Ram
120 GB Ram
650 Watt Antec Earthwatts PSU
He probably meant 1280x720, AKA 720P, a quite common resolution for smaller or budget LCD TV's.
OP, sounds like your system may be overheating.
Try running your CPU and GPU at their stock speeds and see if that fixes anything.
If not, post back you idle and load temps for your CPU and GPU.
Use GPUz for GPU temps and Coretemp or Realtemp for the CPU.