hi: My new used asus motherboard p5b e did exactly the same thing after installing and hooking all the plug ins and ram and graphics card etc.....
All the fans came on , no beep no display wouldn't boot.
Took it apart threeee times put it back together maybe more different things began to happen, ie. wouldn't stay running after hitting power button on, would run for 2 seconds shut off , I think it may be a capacitor on the motherboard which needs replacing/resoldering. By the way none of my capacitors are bulged or leaking.
I would also like to note that I installed a Brand new 600w power source with a brand new 120 gb ssd card to act as my harddrive.
I have to be honest with you, I walked away from it a few times.
At this point I didn't even have an operating system installed yet,ie. windows xp professional.
I sometimes get a little curious when tinkering, and it so happened that by pressing lightly on the square heat sink located below left of my processor the computer didn't shut down right away when power button pressed, it kept running and I got a beep sound. On the down side it stopped when released finger pressure.
On the up side with more experimentation I started getting boot images on my monitor which I didn't have before.
You know the time it takes for computer boot and windows logo to show windows start up, thats how long you had to apply pressure on heat sink.
I have windows loaded and my computer is every bit as fast as I hoped it would be using a ssd as hard drive.
My problem still exists and is annoying, I am waiting for ordered cap tester.