Get two computers, one with a video capture card, and an adapter for converting VGA signal to TV signal. Plug the adapter into the video output of the one you're going to format, then the output from the adapter into the input port of the capture card.
Run the TV/VCR software for the capture card (put it on whatever channel the converter outputs to), then boot the computer to be wiped. You should be getting the output from that computer into the video window on the other computer. (You can even make it full screen so it looks like a directly connected monitor!)
That may be a bit clunky and overkill, but with that setup, you could actually make a VIDEO of FDISKing, formatting, and installing an OS! (You'd have to stop before it tried to detect the monitor, since you wouldn't have one directly connected.)