OK the first thing to try is to whip all of the components off of the motherboard (including memory and hard drive connections). Then try powering it up... Does it beep? If it's working OK it'll go beserk with all the errors (no memory; no graphics card, etc, etc) but that would be a good sign as it shows the motherboard is OK...
If it's still silent, then I would get on to your supplyer and send back at least the motherboard and processor.
If however it starts beeping; then shut it down and add one component (e.g. one stick of memory) then power up. Continue until the thing stops working when you turn it on and you will have found the faulty component.
Good luck and let us know how you got on.
All the best