If you get the "User not Activated" error there is no need to carry out these extensive and time consuming fixes. Just:
1) Plug your Nook into your computer
2) Open Adobe Digital Editions and make sure you can see your Nook above the Bookshelves
3) Select the Settings icon just above it and choose "Activate"
After doing all this I was completely restored - even the current page in the book I had side-loaded and was part way through reading was still correct.