make sure you are using the correct pins for the on/off button. Also make sure power supply is turn on (some have a on/off switch physically on it. make sure it's set to 240 or 120 watt (what ever country you are in). And make sure power cords from power supply are in the motheroboard correctly (ALL cords that are required, as some board requires a 4-pin power cord plugged in, etc).