I have purchased a 700W power source with a 6 pin PCI slot , the Nvidia 560 card I am looking at purchasing has TWO six pin PCI slots in it , am I correct in thinking only one needs connecting to the power supply and the other is to join two video cards for SLI , or do I need two six pin slots in my power supply??
If you already have the PSU, then just get a 4-pin molex to 6-pin PCIe adapter. I wouldn't suggest using three of them (if you wanted to SLI and the PSU only came with 1 6-pin PCIe connector) unless you know what you are doing, since you could put too much current through a wire. One adapter is perfectly safe though.
The unit I bought is a Coolmax CU-700 , it appears to have a red PCI express 6 pin connection and two more 6 pins connectors for peripherals , could I use one of them for the second 6 pin cable?
The Coolmax 700 has two 6 pin PCIe power connectors.
The 2X2 (2 yellow wires and 2 black wires) and 4x2 (4 yellow wires and 4 black wires) connectors are for CPU power. They cannot be used to power a video card. The connectors are not supposed to fit PCIe power plugs. And if they did, you would be shorting 12 volts to ground because they are wired differently.