Change a Windows 8 Product Key

I purchased a large number of Windows 8 Update Keys, but I needed clean installs of Windows 8 on each machine.

Instead of something like "Enter your previous Windows Key" to install it, Microsoft decided to not let the install proceed without the previous version already existing.  I needed a way to change the product key after a clean install with an image copy without installing a previous version of Windows again for every computer.

I found a lot of solutions that sometimes worked, sometimes not.  The one that seemed to work every time for me I found at the Microsoft Community Forums.

The steps are:

1. Run the registry editor (regedit.exe) 
2. Find the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\OOBE 
3. Change the value for the key MediaBootInstall from 1 to 0 
4. Open an elevated command prompt by Running as Administrator
5. Run slmgr -rearm 
6. Reboot your computer
7. Run slui 3
8. Change your product key and activate Windows