The front of your computer is the Front Panel.
The area of contact pins on the motherboard, that the main wires from the Front panel go to, is the Front Panel header.
What you need is a Front panel header pinout.
This I do not have. What I do have, is a simplistic method that may allow you to find out, what the pinout is.http://www.ebay.com/itm/IBM-ThinkCentre-M51-29R8260-Socket-775-Motherboard-w-P4-3GHz-SL7PU-/390456414497?_trksid=p4340.m263&_trkparms=algo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D15%26pmod%3D260995444535%26ps%3D63%26clkid%3D1437936870868306373&_qi=RTM1062688
Looking at the Hardware Maintenance Manual for the ThinkCentre M51, (It also uses this mobo), the Front Panel header is to the right of the Ram Memory slots. (Processor to the left, Ram Memory slots at the Top)
Looking at the Ebay link, there are three views available. Click on the middle view. In the view photo the Front Panel header is the black rectangle below the Yellow ram memory slots.
Two rows of pins.
Power Supply plugged into power, use an LED light with two wires.
Go across the top row, and touch the first set of two pins next to each other.
No? Go on. Touch the next set of two pins. I'm willing to bet the third set of two pins is the Power On switch pins.
(Could be mistaken, however)
The contact made should be brief. The Power On switch is a Momentary Contact Switch.
Once the Power Supply comes on, wait a minute, then start testing the other pins.
LED light blinks? You have the HarDDrive activity LED pins.
LED light stays steady? You have the Power On LED pins.
Be aware however, that there may be 3 pins for the Power On LED.
Two Positive ( + ) pins, and one Negative ( - ) pin. This is for a dual color Power On LED. (Turbo mode/ Regular mode)
This would mean touching the first pin, or second pin, in the set of 3 pins, and the last pin in the set.
Computer restarts? You have the 2 pins for a Reset Switch.
(Do NOT touch the Power On switch pins again, or the computer may restart)
Not what I would like to state. Would like to state the exact pinout.
Perhaps if you get this figured out, you might take the time to post the pinout. Crude is fine, I can 'clean it up'. This way 100's to 1000's of people may be able to use your findings. Think how many people you would help.