Probably a short somewhere since it turns off immediately after turning on. I would check all your connections, make sure the 4 or 8pin CPU power cable is plugged into the board from your PSU, the connector is usually near the top right of the mobo. If that doesn't solve it, pull the mobo out of the case, put it on your mobo's box or something and try to turn on the pc outside of the case, if it turns on you likely have an unused standoff in the case touching the bare PCB of the mobo, or there is a short somewhere else in the case.