ed have you checked your power supply. one time my comp would freeze up a lot but only in games. and i couldn't figure it out i tried different video cards. and it still did it i though it could be my mother board so i brought it in and had it benched marked and it passed. so i was told that a video card need a certain voltage to work right or they will freeze comp. turns out when a load was put on my video card it drew to many volts for my power supply because it was old. got a new 430 watt power and never a lock up again just a thought. i have xp and no problems. with the nvida detonator drivers.