cant change resolution & screen flickers

[j10jep2]

hi there

i try to start the game and "Could not set display mode and 640x480 is used instead!" comes up. then i get into the game at that resolution and the graphics are all flickery like im watching an old VHS tape or something i thought it was part of the main menu until i started a game and the game graphics were a flickerin too! i'm using the most stable video card drivers i could find. newest drivers for my geforce go 7600 make tf2 and l4d unplayable so im using the next to newest drivers because they work fine in every other game i own. is there some way to fix this