No POST on Boot.

Ok, my bro gives me his pc saying when he turns the power on, nothing happens. So i say ok and take it to work on. When booting there is no POST. No error beeps and no video. I remove all the periphials trying to provoke a beep of some kind out of the board. Nothing still. I figure, well maybe the board has died. A trip to the pc store and im able to find the exact same board he had already. I swap the boards out, replace everthing where it should be. Power the system up…. the same thing. NO POST! No beeps, no video. I even tried clearing the CMOS on the board. Nothing. Any ideas would be appreciated. Thanks!