Orient the motherboard so we are both looking at it the same way;
Processor to the Top, black and white Ram Memory slots to the Right, white PCI slot, and black PCI Express x16 slot to the Left;
Above the white Ram Memory slots, is the 4-pin ATX +12 Volt power cable connector. Whitish, square, 4 socket hole connector.
General example of this power cable, and it's respective connector,http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4
Right next to it is a black header.
The Front Panel header, (Panel1)
This is the pinout,
Scroll down to Dave G's post.
4 pins across one side, 5 pins across the other side.
The side with 4 pins has the pins numbered EVEN.
The side with 5 pins is numbered ODD.
START on the OPPOSITE side of the missing pin.
As you can see there is -> No Pin 10.
The pin on the other end is Pin 2.
Pins 2, 4, 6, and 8. No Pin 10.
Pins 1, 3, 5, 7, and 9.
A) Pins 1 and 3 are for the HarDDrive activity LED. (Light)
Pin 1 is for the Positive ( + ) wire.
If the HDD LED is dim when the harddrive is active, switch the wires around.
2) Pins 5 and 7 are for a Reset switch, IF a Reset switch is used.
3) Pin 9 is N/C. Not Connected. Reserved for the factory
4) Pins 2 and 4 are for the Power On LED. (Light Emitting Diode)
Pin 2 is for the Positive ( + ) wire.
If the PWR LED is dim when the computer is on, switch the wires around.
5) Pins 6 and 8 are for the Power On switch.
6) No Pin 10
The above is a PDF file, Illustrated Parts and Service Map, of the HP Compaq DC5850 Desktop PC.
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For additional questions please post in a Comment.