I have a Nvidia Geforce 640 GT. I built the computer in November. The DVI port shows only a black screen but the vga port works. I am trying to run another display off of the DVI and it isn't recognized. I am using an adapter for vga into the DVI port and tried a DVI cable with a vga adapter on the end. I have uninstalled and reinstalled the driver twice. I am stumped. Any ideas would be great. Thanks