Graphics card problem

I run a two year old NVIDIA Geforce 7900GS and play two games, San andreas Multiplayer and Counter-Strike: Source.
In ALL games the game completely messes up and it is black, the textures stretch, trees become magically high the display messes up, finger nails become long. The screen flickers black and FPS drop to around 10, it’s completely impossible to play.
The graphics card is fine in Windows, although when I first boot up at the top of my screen there is a few lines going across (white lines)
Is it my gfx card or my monitor? The cable between the PC and the Monitor is faulty, but i don’t really care. Just wanna play game.
The flickering etc doesn’t happen all the time just sometimes, the grasphics card is NOT overheating and is clean of dirt.
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hope someone can help me, thank you very much.
ALL DRIVERS ARE UP TO DATE BY THE WAY, SO IS DIRECTX9.
Answer #1
could be overheating
whats the avaragre temps
and have you overclocked?
Answer #2
No I haven’t overclocked and i’ve just said it’s not overheating mate, it’s 43c
Answer #3
test other games and see what happens, could be the cable problem maybe run a stress test on the GPU and see if it still occurs. Play a movie/video and see if it does the same as well