Start with a 'bench test' of your motherboard. strip it down to the bare minimum thugs to let it boot. Use the built in VGA monitor port, it it has one. No GPA card. No RAM but one stick. No printer, no CD-rom no HDD. No keyboard, no mouse.
It should boot quicker and get the 'no keyboard' error.
After that, start adding things. Also, try the default settings in BIOS. Does the board have the right time and date?