Power Supply always on

If the power supply is getting juice all the time, no matter how many times you press the button but stops getting juice if it's disconnected from the motherboard, then the switch is bad.

It's not the switch. I've checked two power supplies on the new motherboard, and both times they turned on by itself. Then I've checked the same two power supplies on good motherboard (took that chance cause was eager to find out) and it worked fine. So it is motherboard, but not sure why it's doing it. And power button has nothing to do with it.

Maybe I wasn't clear in my description so let me try it again. I made the mistake of using the term switch to mean the power button. So, from now on, I'll call it the power button. There is only one way to eliminate it as the cause, is to connect everything and while it's running press the button and hold it for 5 seconds. The PC should stop. If it doesn't stop, disconnect it from the mother board completely and see what happens. If the PC stops running the button is bad.

That's the only way to tell if the power button is bad or not. There is no other way.

I second that...

I already RMA'd the motherboard. The new one solved the problem, works flawlessly now.

Thanks for help everyone, but it wasn't neither the power button or the power supply.