Has any attempt been made to overclock the system or have there been any power outages or spikes previous to this happening.
Couple of initial troubleshooting suggestions for you to check for us;
1: Your MB has two video card slots, try the video card in the slot that is not presently in use.
2: I do not see an onboard BIOS speaker on the MB diagram but do you normally hear a single beep when the POST normally completes successfully, if you do please remove both sticks of Ram, reassemble the computer, turn on the power and see if you get any error beeps.
3: In case of a bad MB setting remove the CR2032 battery on the MB for a while and then replace it, this will restore the MB back to the default factory settings, see attachment below.
Post back with an update when you have completed the above.