Question: I have discovered this problem with my Laptop, today itself. No matter what the environment, app, screen is, as soon as I press **CAPS LOCK** key, the computer shuts itself down abruptly (abnormal shutdown, like power failure). 

It can again be turned on normally though, using power button.

I Googled a bit and discovered that CAPS LOCK is used as CRUISE control so it shuts down the laptop in-case it is not cool enough. My laptop is cool enough.

Following are the environments, in which I've tested this abnormal behavior of CAPS LOCK (abruptly shutting down my machine)

1. GRUB
2. UBUNTU 16.04
3. System Testing (F12)
4. Windows 8
5. Pressing CAPS LOCK on on-screen keyboard
6. External Keyboard's CAPS LOCK

My laptop is **Dell Inspiron 3542**. Thanks

Answer: 
I had exactly the same problem. In my case keyboard replacement in laptop (Lenovo ThinkPad T420) solved the problem.
Have you tried by enabling **Toggle Keys**? I don't know if this will prevent the laptop form shutting down but I have other kind of issues using the Caps Lock and by enabling it solves some problem. There's nothing wrong to try. Please follow these steps:

1. **Open Ease of Access Center**, by typing it on the search bar.
2. Now click **Make the keyboard easier to use**, this will open a window.
3. Check **Turn on Toggle Keys** option.