jnorsworthy I don't know if the design still holds the same for the Power On switch in the Slimline S3100N, as it does for the Power On switch designs I am used to.
[The Power On switch is located inside the plastic Power On button ]
The one I am used to;
1) Has a square block like shape.
2) The square block is composed of two halves. The two halves fit together like a clamshell.
A) A metal cover with a hole in the center for the top half.
B) A plastic block for the bottom half.
Inside there is a 'plunger', if you will.
The plunger, or post, moves up, and down.
The post is allowed to move up, and down through the hole in the top cover.
The plunger presses against a thin, flat, disk, convex shaped piece of spring metal.
The outside edges of the metal disk are connected to one side of the Soft Power On circuit.
As the plunger is moved down (By the action of pressing against the Power On button), the metal convex shaped disk flattens out.
In the center of the plastic base is the other side of the Soft Power On circuit. The center of the flattened out metal disk touches a contact in the bottom, of the plastic bottom half of the switch.
When the Power On button is released, the disk goes back to the convex shape.
This generic ATX power on switch, is an example of the type of Power On switch I am referring to,http://www.directron.com/atxswitch.html
You may find the above generic example is a replacement for the one in the Slimline S3100N.
This is HP Support, the support page for the HP Slimline S3100N desktop computer, and the Manuals page, http://h10025.www1.hp.com/ewfrf/wc/manualCategory?lc=en&dlc=en&cc=us&lang=en&product=3440586&
On the above page scroll down to the heading - Upgrading and Servicing Guide, and left-click on it.
(It's a PDF file, and may take a few seconds to download. May take a few seconds before you see the first page)
Shows how to open the computer case, and remove the Front Panel. (Front Bezel)
Computer unplugged from power, Observe Anti-Static Precautions.
Your body carries Static electricity.
Static WILL fry out (Short Circuit) the hardware components inside a computer.
1) Work on a table
2) Computer unplugged from power, computer case open
3) TOUCH the metal frame of the open computer case to relieve your body of Static
4) If you leave your computer in the middle of working on it, be SURE to touch the metal frame again upon your return.
Most Power On button assemblies have two tabs, or three, that protrude out from the body of the assembly. These tabs snap into place into the metal frame of the computer case, and into a rectangular hole. They have a hook on one side. Gently squeeze the tabs in, or out. Depends on which way the hooks face.
The plastic Power On button assembly generally has tabs that hold the Power On switch in place. These tabs are eased over to allow removing the Power On switch. You may find that the plastic tabs are brittle due to age, and the heat inside the computer through the years.
You can use a hair dryer set to low heat, and wave the hair dryer slowly back, and forth to soften the plastic.