Hello; It is possible that a particular device is preventing the system from accessing the operating system . For testing purposes, please uninstall all devices except for the CPU, minimum amount of system memory and the video card. Remove the USB keyboard, mouse, hard drive ,front panel, optical unit and test the system with the minimal configuration If the issue is resolved, then proceed to add one device at a time with subsequent reboots to determine, which device is causing the problem.
I've done all that. Still no POST. Just a blank screen, monitor not even getting a signal from the (built-in) video. I think the board is toast as I've done everything I know to do.