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The main 24 or 20+4 power connector is not the problem. On most boards you see two small blocks of tiny pins pointing upward where the wires coming in from the front or top panel for the power button, reset if one is seen, power led, and hard drive activity led go on.
Those are generally found at the bottom edge of the board opposite of the pci slots. Sometimes those are separate individual wires tagged with some harnesses while others will have two wires going into a plug with lettering like the one seen in the photo here.