So this might be a silly question but did you plug the power from the PSU into the six pin connector on the card? The plug on the top back corner of the card.
No

My PSU does not have a 6 pin PCI-e wire. The dual 4 pin molex to 6 pin PCI-e adapter which came with the GPU isn't much help since this PC does not have 4 pin molex wires.
Spoiler :
The PC does however have 1 SATA power wire left (thats the correct term for the power wires which connect from the PSU to the Hard Drives and CD/DVD drives right?)
Would this:
http://www.amazon.com/Branded-8inch-15pin-Express-Power/dp/B005NJXY7O
Be able to convert the SATA power wire and deliver enough power to the GPU?