Magical Jelly Bean key finder and and others like it, as I have just learned, do not work with Windows 2008r2 because MS has encrypted the key in registry.
There are a few pay for programs that can retrieve the key for you, but luckily someone much smarter than me has written a very succinct PS script that returns the key, unencrypted 🙂
You can find the code here, or copy it below.
Look in the comments of the above linked page for specific instructions on how to save and run the script (if you’re not to sure on powerscript)
Don’t forget to run