It's a bugger if you have an LCD monitor because you have to setup the frequency accordingly. If your card has a TV OUT, try to plug it to your TV to see if there is something. If you can, access you BIOS and change your AGP aperture size; by default it may be to much. Then is when you start up (still using your TV as monitor), reboot in safe mode and set your display to the LCD default settings. If it still doesn't work, do to your display properties and check the option box to reduce DVI frequency.
NOte if your video card does not have TV out, try using another monitor! to change your settings.