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