problem

my problem is in l4d not sure about tf2 cause haven played it for awhile anyways when i play my game will freeze up then i ctrl alt delete n im able to go back in and play again as if i haven crashed recently my texture were flashing random colors so i thought it was the driver so i reinstaled them any ideas on how to fix this

im currently useing a

evga 9600gt 1 gb

evga 790i ultra mb

950 psu

ocz ddr3 4 gb

intel core 2 duo