I've checked my manual for this and I am quite confused, there's a gap between the two sockets and the cable is a two pin.
Is there a particular way to plug it in? :S
(My motherboard is an Asus M5A78l-M/USB3)
P.S: I'm not very good with computers : L
I think I see your problem, The connector at the end of your pled is only 2 pin, where as most others are 3 pin with nothing connected in the center. You can remove one of the pins from the plastic connector using a needle or a precision screwdriver. cover the outsides of the pin you removed with electrical tape so you dont short anything out. then plug them in using that diagram above.