The eMachines C2685 uses an FIC VC37GV motherboard. (First International Computer, Inc.)http://www.motherboards.org/mobot/motherboards_d/FIC/VC37GV/
Here is the motherboard manual,http://www.ime.org.uk/pdfs/vc37_vg31_b1_eng.pdf
After you click on the above link, give it up to 30 seconds to download. This is a PDF file.
Barring you cannot download the file, I will state the connections for the Front Panel header on the motherboard.
(Plus state the page to reference to, in case you can download)
View the first link, with the photo of the FIC VC37GV motherboard.
As shown, Processor is at the top, Ram Memory slots are to the right.
The Front Panel header is located at the very bottom right corner.
It is parallel to the outside edge of the motherboard. There are two rows of pins.
The Front Panel header has 5 pins going across the top, and 4 pins across the bottom.
The top row of pins are numbered Odd.
The bottom row of pins are numbered Evenly.
On the Top row starting on the Right side, going towards the left, the pins are numbered 1, 3, 5, 7, and 9.
On the Bottom row starting on the Right side, going towards the left, the pins are numbered 2, 4, 6, and 8.
A) Pins 1 and 3 are for the HDD LED. (HarDDrive activity LED)
B) Pins 5 and 7 are for the Reset switch
C) Pins 2 and 4 are for a Dual Color Power On LED, if used.
Green goes to Pin 2. Yellow goes to Pin 4.
Otherwise Pin 2 is Positive, ( + ), and Pin 4 is Negative. ( - )
D) Pins 6 and 8 are for the Power On switch.
(PWR1, or SW1)
There is a small 3 pin header, just above the Front Panel header. (Page 12)
This is for a Power LED that has either two wires, or three wires.
The pins are numbered from Right to left.
Pin 1 is for the Power LED, and Pin 2 is for Ground, if using a two wire Power LED. (Not dual color)
Pin 1 is for the Power LED, and Pins 2 and 3 are for Ground (GND), if using a three wire Power LED.