Remove everything from the mobo, including the CPU, fans, VGA etc, and only connect the power cables and the front panel headers for the power switch. Then try turning it on.
It aught to beep to tell you to insert a CPU. If not, it's either the mobo [not installed correctly? standoffs all in place? etc. you know, usual suspects] or the power supply.
If it does beep, then plug in teh CPU. If it still beeps after tat, keep adding components till it stops beeping. When it stops beeping and returns to the current form, that's probably the faulty part.
HTH.