My Video Card is not working properly?

Ok - so I can load my CPU in a VGA mode - or when I turn it on, the monitor displays. I have nVidia7900GTX and once that begins to be used by my CPU, the monitor goes to idle and black. No signal is being sent to the monitor. Any ideas on how to fix this or is my video card bust? Thanks!|||Have you tried updating your drivers? Go to NVidia.com to find support for your card. I just bought my computer a month ago and they already had a new driver for my Nvidia card.|||Does your motherboard have an integrated video card? You may need to disable that in the BIOS before the OS will recognize the video card.