Serious problem with game graphics

For as long as I can remember, my Nvidia NX7900GTX has been making incredibly annoying graphic tears or polygon stretches or whatever you want to call them:



But guess what, those pics are from my brand new ATI hd 4850. It also happened with a 4350. It seems this problem is caused by something else and I have no idea what; I know it's not the processor as I just bought a new dual-core. Google has been no help. Please, can anyone help!!

My case is well cooled.
Motherboard: 775dual-vsta (Quite old)
RAM: DDR2 667 2GB
HDD: 2x 160GB Western Digitals (One of them brand new)

Please let me know if you need anymore info.
Also this is a fresh copy of windows.

I have always had my settings(driver+game) to the lowest. The only thing that seems to affect the tears is when I minimize or adjust the game in any way ie. change one mundane setting in game. They mostly go away but soon come back.

I haven't tried memtest though I'm sure RAM isn't the cause.

Though one thing I should note, the new radeon 4850 has improved my graphic tears significantly from the 7900gtx. But they still exist.

Also I have not reformatted since switching off the 7900gtx, could it be left over nvidia drivers in the system? Thanks for that speedy reply

It happens in many games.

Well, if not a clean install, you should run a driver sweeper in safe mode just to be sure it ain't remaining nvidia software.

And another one shooting in the dark!
I suspect a corrupted install: Either DirectX or motherboard drivers.
Dowload the motherboard drivers from the Asrock site and reinstall, also, DirectX does not update along with Windows, go to the Microsoft website and update it from there.