Problems with my geforce 6600 driver problem maybe? flickers HELP

[AVAFREAK182]

Well I bought this GeForce 6600 of of Godm@n here, and its having problems. I installed the "latest" drivers from Nvidia's site, but still when I start to play HL2 it says "You do not have the latest drivers blah blah blah". I click continue anyways, and it goes into the get, and right as it gets to the menu, it has a fatal error, and clicks out. Also, when I click the Nvidia control panel on my startup bar, the video card flickers as well. It flickers whenever there is a main change in the screeen. Any ideas?