Not enough USB 2.0 headers

So, I am currently building my new computer at the moment and I have built several computers before but I have ran into an issue I have not encountered before. My case is the phantom 820 and has three usb 2.0 connectors however my motherboard the asus crosshair v formula z only has two headers on the motherboard. I have noticed that 2 of the 3 connectors seem to have two cords cords running into the back whilst the other only has one - will that make any difference - I can upload a picture if I am not describing accurately. Is there anything I can do with the spare USB connector left over?

One of those is probably the USB 3.0 header. If 2 of them look/are the same, then those are probably the 2.0, while the other cable is the 3.0.

No my USB 3 connector cable is very easy to tell apart as it has a significant amount more pin holes and the manual made it very clear where that is to go. Those three cables I was talking about are all labelled USB 2.0 , I think one might be my card reader though with just a misinformation.

Possibly - I would have to see it to be sure.

So I am pretty sure it is the card reader as there are four USB2.0 on the front panel and with two cables running into each connector that'd make sense. Another question though, which makes me feel really dumb >.> I have cables left over from my PSU... I have never encountered this before either, With a modular PSU is this a common occurence and also should I plug in the molex pin near the PCI-E slots with only one graphics card (using 7970 direct CU II)? I have it plugged in currently but I am pretty sure I recall hearing that it wasn't necessary unless running crossfire or SLI.

Thanks for the help >.> Makes me feel a bit embarrassed considering I have built several computers and have a few certificates in the IT field.