Try a naked boot first to see if the it will run without any drives attached.
Run the mobo with just one stick of ram,videocard,cpu and no other devices.
Will the pc boot and can you get into the bios?
Make sure the cpu, ram and videocard are all seated properly.
Are all power plugs connected? Videocard...cpu.....?
Have you tried clearing the cmos?
If the motherboard is in your case already is it accidentally grounding on the case?
Just some basic suggestions since we have very little to go on...
