Monitor won't display after video card upgrade, single post beep.

[Idesofmarch]

I just installed a new GeForce 6800 video card, but upon reboot the monitor will not display anything. Removal of the card causes the computer to run fine, but reinstalling the previous card causes the same problem. It gives only a single POST beep at startup and the computer sounds as if it's running properly (the keyboard and mouse respond as usual) but I can't get any sort of visual, any help?

 

[temporello]

Do you connect your monitor to the new card?
Check your bios settings (you may have to disable onboard video).

And btw,how can you tell this without seeing anything on the screen: "the keyboard and mouse respond as usual" ?