Several of the power supplies I have have an odd connector Ive never used. Its flat with 6 pins, 3 black wires, 2 orange and one red and usually says P2 on it. thanks

Your answer

Those are the plugs that connect your power switch (you know that button you hit to turn on your computer) and also they connect your led lights for you hard drive and power led. Hope that helps.

This one http://www.halted.com/ccp16659-6-pin-power-connector-for-computer-power-supply-con-60001-gen141.htm

It looks like

it looks like a p9 or p8 connector. those are the power connectors for the old AT form factor motherboards. At least that's what it looks like to me.

It looks just like those but its smaller. I found several sites where its called an ATX2 connector but nothing that says what it connects too. Thanks anyway.

This connector I've only ever seen on OEM PCs like Gateway and Dell. Most all retail motherboards do not use it. I guess you may even say it's the precursor to the 4-pin or 6-pin extra connector we're used to using these days.
Because the black wires should be ground, red 5V and orange maybe 12V? Similar to the extra plugs we use now. It's used for extra power.

But again, I don't see that on any retail motherboards, nor do regular retail power supplies have it. But I see it on OEMs a lot.

Yet another nonstandard approach the big boys use to screw the little man. Forcing you to buy a new power supply from them, because generic ones don't have their special connector.

Those flat connectors (often called AUX) are for high-end/server motherboards, that quite often have 2 CPUs on them, and thus need extra power.

Thanks you!