Laggy HD Radeon 6950

[TopLuca]

I have a major problem with my graphics card , I've got this HD Radeon 6950 for the past 6 months suddenly a few days ago it started lagging all over the place even when playing videos over the media player or even youtube , same with games like MW2/3 which I used to run over 100 FPS so what I did is updated the drivers and it worked fine for a day and then the problem arose again and it started lagging again , what should I do and what would be causing this lag ?
Thanks

The Model is XFX 6950 2GB DD

 

[wanderer11]

What is the temperature when it starts lagging? Use gpuz or hwmonitor for that.

 

[TopLuca]

Usually the problem lies when I startup my PC with my HDMI Plugged in my GPU but if I started the PC with the D-sub then switched to the GPU Nothing happens but anyways the temp is around 70 Degree Celsius