Computer Doesn't Boot if Graphics Card is Installed

After I flashed my BIOS (should not have done that without knowing what I'm doing) my computer wouldn't start, so I gave my PC to computer repair shop. They flashed it again and now it only boots with on-board graphics. If the graphics card is installed the computer is not booting up. Even if the VGA cable is plugged into the on-board graphics. The fans on the processor and the graphics card spin up but there is no display on screen. Also the graphics card does work on other motherboards.
 
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