Also, just remembered...I once had symptoms like yours long ago...the board would reboot around after 5s after power up with no video, I had a embarrassing n00b moment and connected the power and reset button connectors wrong on my board, didn't damage the board just made it act like yous. Also thought it was graphics card BTW.
Never over underestimate the power of dumb.
Never over underestimate the power of dumb.