So i built a gamer / school puter for my bosses son. All the parts arrived today and i installed them into the tower. I have built a lot of computers before but this one does have something i didnt come accross until today. The ATX power cable from the PSU is smaller than the ATX connection on the MB. It fits in there still, but only one way and it leaves 4 pins un-used. I still put the ATX12v ( small square one) connection in its usual spot on the MB. Also, the little clip on the ATX connection that locks into the same connection on the MB doesnt line up. I did plug it in the way it fit, but it didnt lock in. The MB has a green light on it that is "ON" but pushing the power button on does nothing. I have check the Pwr Sw, HD Led and Reset Sw and they are correctly done. My only guess is i did something wrong with the ATX power connection or the PSU is bad. The light on the MB tells me the PSU is most likely ok so i am at a loss. The PSU does show 115 volts selected and the switch on the back is also correct. I moved it to make sure and it still didnt turn on. So what is the skinny on the ATX plug on the MB being larger than the connection from my PSU and could this be related to my problem. Andy Wanna kill these ads? We can help!