Still need more info. What troubleshooting steps have you taken? What were the results? Are the proper power connections plugged in? Are you sure the PSU is working properly?Did you connect the on/off button to the motherboard properly? Did you use the brass motherboard stand-offs? Did you use paper washers between the brass stand-offs and the motherboard? Is the mobo new or used? If used, was it tested and guaranteed not to be DOA? Do you see any blown capacitors or are any capacitors bulging?