No Video Signal

I just installed a geforce FX5200 graphics card into a Dell Optiplex GX240 mini-tower. Upon rebooting, I had no video signal – it was as if the monitor was not even connected to the computer. I shutdown and reinstalled the original card and everything worked fine. Yes, I uninstalled the old drivers first before installing the new card. Could it be the power supply is not powerful enough? There is a very small power connector on this new card that is not present on the original card – does this new card require an additional power source?

Any suggestions?