'Spring Cleaning' (your computer)

When throwing something out, like Firefox!, after you do your thing in Programs and Features, go into C:\Users\yourname\AppData, and look in both its Local and its Roaming folders for 'Mozilla Firefox', and delete both of those so that those can't come back to bite you if you ever want to re-install it in future when it will be revised and improved beyond recognition. Or very close to it.

Then, start a Command Prompt with Administrator Privileges, and run the following commands, as shown in this screenshot, which you can click to enlarge...

This restores your Windows 8 to its original factory image, and makes sure that everything is in its proper places, just as if you did a re-install of it, except that you don't have to replace any third-party bits, and it doesn't take nearly as long as the re-installing would. You're 'good to go' in just a few minutes. And this is one of the smarter things Mighty Microsoft has ever done. Thanx, MM...