I was recently gifted an HP Elite 7500 i7 Microtower and am trying to install a GeForce GTX 670 graphics card. I have placed it into the PCIe x16 slot fine but upon startup it tells me the card needs more power and to plug in the additional power cables. Herein lies the issue, I cannot see where the external power cable connects to my PSU, so any assistance on that would be most appreciated.