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
Check and see if your DVI port on the card is digital/analog or just digital only. You will need a DVI-I port to make analog work through a VGA adapter. Here is a chart to distinguish the difference. http://www.entechtaiwan.com/images/dvicon.gif
DVI-A or DVI-I would work with a vga adapter since they both include analog signals. A DVI-D port is pure digital and will not work with VGA without an active converter box and for the price of that you might as well install a vga card.
Also please be aware that the DVI cables need to be considered too. For example a DVI-D cable will fit a DVI-I port and VGA adapter but wont transmit the analog signals since it doesnt have the wiring.
Lastly check the specs on your card, I remember something about it being only to display analog thru 1 port only so you may never get 2 analog monitors to work with it.