Installed new video card, now no display!!

Just installed the new low profile 9600gt galaxy card into my dell c521, which previously had the ati x1300. I am getting a blank screen when I start the computer. I get the click noise from the monitor like I usually do when I start the computer, but there is no display on the screen. I hooked the x1300 back up and it worked fine. It also works fine when I use the onboard video with the 9600 uninstalled. However, if I have the 9600 installed, and have the onboard video plugged up to the monitor, the screen tells me that I have an unsupported video configuration and to turn off the computer, switch the cable to the new video and restart. Of course, when I do this, I get no display.

I already have the card hooked up to the power supply via a 1-molex to pci-e adapter.

You need to be using a TWO molex to 1 pci express adapter. One molex from one rail of the power supply is probably not giving it enough power.

Drivers...yep...definitely need the correct drivers.

Also, you may want to verify that your PSU can provide enough power to that card. I didn't find any specific info on the 12V rail(s) for that 280W PSU on the Dell site. Might be on the PSU itself though.