How to replace your PC's power button with an arcade pushbutton

I'm building an arcade cabinet using the fantastic kit from North Coast Custom Arcades.  When it's done, the PC at the heart of the project will be entombed in a classy wood enclosure.  Now I need a way to turn the PC on and off, without unscrewing the wood cabinet, that maintains the general look and feel of the rest of the project.

So I've replaced the PC's power button and status light with this very nice chrome-accented, back-lit button.  And frankly, if I can do it, so can you.

What you'll need:

1. A cheap tower PC.  I have no idea how I'd do this with a laptop or compact desktop.
2. A button.
3. Some cables.  I happened to have the Extension Harness Pack from Ultimarc on hand, which is pre-terminated with exactly the lengths and connectors I needed. Or you could chop up the cable that's running to your old button and re-terminate it with these.
4. The willingness to put a 1 1/8" hole in something.  I like my Forstner bit for that job.

OK, let's do this thing.

Unplug your PC and take it somewhere well lit.  Keep the AC unplugged until you're done poking the motherboard, please.  Tear the side and plastic front off your PC.  You'll end up with something like the picture below.  The black plastic cube on the right, below the DVD, is the mechanism behind the shiny power button facade.  That's what we're replacing.

Use a camera phone to peek around inside the PC, behind the old button.  In person, it was obvious that the red and black cables are for the button, and the blue and green cables are for the power LED.  The yellow and white cables are for the hard drive indicator, which I'm now living without.

 Now follow the bundle of cables from this mechanism to the motherboard, and make note of what order they go in.  Here, it's green, blue, red, black.

Now unplug this end from the motherboard, and remove the old button from the front of the PC.  (Mine just snapped on.)  If you're reusing this cable harness, now's the time to chop off the old button and add those female QD terminations.  If you're using the Ultimarc wires, throw this bundle away.

 Now, take your button apart.  The whole switch-and-LED assembly turns a few degrees then slides out of the chrome jacket to make this easier on you.  The switch mechanism is the big black box, wire black to COM (the bottom connector) and wire red to NO ("normally open," the next connector) and leave the top connector alone.

 Now wire blue and green to the LED contacts on the sides.  I couldn't find any indication of the correct order, so I guessed.  If you get it wrong (button works, light doesn't) just unplug and swap, you won't hurt anything.

Now if you're using the Ultimarc wires, fit each wire directly onto the motherboard pins.  It's fiddly work, but if you're patient it's over quick.  If you cut and re-terminated the original wiring harness, good for you, your hard work on that step makes this step a breeze.

Time for a bench test!  Grab a monitor, and plug in your PC, then push on the teeny button alongside the LED shaft (next to my thumb here).  On my PC you have to hold it for a second, don't get antsy. 

That's what success looks like!  The fans warm up, the light comes on, and moments later the monitor fills with the lovely BIOS screen.

OK, now you can drill a 1 1/8 in hole in your cabinet (or use one of the pre-drilled button holes.  I wanted this out of the way, on the back near the floor) and mount the chrome body of the button. Then put your PC back in the cabinet, and snap the switch-and-LED assembly into the chrome button body.  Gorgeous!