For any issues with the First Edition you should turn the reader completely off (not the standby mode that shows the "screen saver" pictures) and try the procedure you are having problems with after turning the device back on (you should get a screen crediting Adobe Systems for the reader software during the restart process). You should be able to learn more in the electronic user manual under "My Documents" on your reader (should also be available for download from B&N's web site).
I'd suggest installing a reader application on a PC (if you have access rights to install software on one), logging into your B&N account with the reader application and downloading your books from within the reader application one at a time. After downloading each eBook see if you can read it with the PC reader.
I don't have any experience with B&N's reader applications for Macintosh, iPad/iPod, or Android Phones/Tablets, but you might be able to accomplish the same testing with those versions.
I recommend using the "archive" function on your books instead of "delete". When your hardware Nook syncs with B&N's servers archived books will still be listed, but their contents will not actually be stored in the reader. You could also test each individual book by archiving the books and retrieving them one at a time using the interface on the Nook testing each book before retrieving the next from archive. If you use the "delete" function you might have to pay for your book a second time to download it again.
Note that some eBooks and ePeriodicals (Magazines and newspapers) only work with Nook Color and Nook Tablet. Check the B&N sites Nook books listing for device compatibility for each publication (look near the price)
