B&N seems determined to go out of business.
I have some books I recently purchased from B&N (girlfriend gave me a gift card at xmas) and would like to back them up to my Win7 PC, etc., but cannot even see the files. All of my side-loaded ebooks are visible, though. If there is some kind of hidden partition on the Nook, I don't know how to see it.
I cannot see myself giving B&N any more business in the future.
Edited to add: Looks like I have a Win10 laptop coming my way at work. From the posts above, it sounds as though if I use the B&N Windows for PC app on that, I should be able to grab my book files. So... that is good, but BLEEP those BLEEPING BLEEPERS at B&N for making this necessary. Part of why I bought a Nook in the first place was to avoid Amazon. Now, it turns out that Amazon has the more easily accessible and manipulable file structure.