if there is a old working PCI (not PCI-e) video card i would try to start the rig with it. usually when the VGA dies BIOS beeps in a special manner. but sometimes died VGA blocks the BIOS and it's unable to beep. so i would focus on VGA. trying another VGA, trying this one on a different rig, and trying with PCI card in case of PCI-e port dieing.