No display on my computer monitor after installing me new nvidia gtx 460 graphics card?

OK, her's how it is. I installed the video card and powered up the computer, I hear the windows login screen like normal, but there is no picture on the monitor at all. I have an ati radeon 4200 hd integrated into the mother board, if that helps. Am i supposed to disable the onboard graphics before installing the gtx 460? Or is there a way to install the drivers into the card before installing it into the desktop. I am using a 600 watt power supply by Corsair, so power is not a problem. Please help!!! I tried plugging the hdmi cable between the new card, and the computer monitor, that did not work. I even tried plugging vga between my onboard graghics and the monitor, that did not work either after i installed the new card