did you download the lastes video card driver for your nvidia geforce 6600?
if not try that to disable the built in video card go to control panel-system-hardware-device manager-display adapters and there you should see you built in video card right click it and say disable then you should be fine
tell me if that works
I got a new graphics card and it freezes my computer after 2 minutes after startup I don't know what to do and my other card was built in and when i disable the one I have in it doesn't detect the one that is built in.(i got a new one because the one built in is a 8mb)
New gfx card: Nvidia GeForce 6600
AMD Semprom Processor 3300+
Plug and Play monitor