One way to see if the board is grounding out or even the actual problem is to isolate it entirely from the case itself. A circle of simple rectangular pencil erasers can easily isolate the board from even non conductive surfaces where you try it with only the video card, memory, cpu, and supply to see if the board is good. If it then sees a normal post to the point of seeing no boot device found the board was grounding. If nothing but a quick spin of fans is seen the board needs to rmaed for a replacement probably from bad caps.