steps you would have found the problem before you had everything connected.
Before telling you to strip it down the the bare minimum, make sure that you have the CMOS jumpers on the correct terminals.
We may have to go back as far as to check that the mobo is not shorted out to the mounting plate.
Is this a new mobo in an old case [one where a different mobo once resided???
First step would be mobo mounted, Power Supply connected, CPU w HSF, one stick of memory. NOTHING else except the case controls connected to the mobo. No video card, no monitor, no keyboard, no mouse. no drives.. Should get lots of beeps because you have no video, no sound card, no modem, no PCI cards of any type.. Get that far and then we add video and monitor ONLY. Get the single screen that shows the video card and sometimes the BIOS data. Don't get that far and there is not a heckuva lot pof things to trouble shoot.
Disconnect the signal and power cables from all devices.
The motherboard in the PC I just built fails to allow me to enter BIOS setup. I installed an Asus A7N8X-E mobo with an AMD 2600+ CPU. When I power the thing up I am stuck at the ASUS "cover". Repeated attempts at pressing "delete" get me nowhere. Also, I do not seem to be getting any power to my optical drives - (if that matters). Thanks in advance for your assistance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic