Hi,

a normal procedure is to unplug everything until you only have:

power supply, motherboard, a single RAM module, processor with fan, a graphic card and a keyboard. In this minimum configuration the PC has to start....graphics bios....bios....no boot device found.

If that configuration works, bit by bit plug everything back in until the failure shows up again and you have your "troublemaker".

If the configuration does not work, take another graphic card....try if it works. Take another RAM Module.........try if it works. Take another keyboard......try if it works. Take another power supply..............try if it works. If it still doesn't works its the motherboard or the processor.