Answer to your question below, but as you will see it is quite hairy if you are inexperienced.
Might be easier to install ADE 1.7.2.
- Return the book.
- Make sure ADE NOT running.
- Find the mainifest.xml file. Probably in the Documents/My Digital Editions directory, which is probably where you found and deleted the .epub file.
- Edit the file with any editor. For example, Notepad, though that is rather awkward for this file. If you have it, something like Notepad++.
- Find the <de:contentRecord> section relating to your book. (details below *** for 4/5/6/7 with Notepad)
- Delete that section.
- Save the file.
- Run ADE and see if you can borrow the book ok now.
*** to edit with Notepad, steps 4/5/6/7
- Make a safe copy in Explorer in case you mess the rest up. Select mainfest.xml. ctrl-C. ctrl-V
- Right click on the file in Explorer
- Choose 'edit'
- In Notepad, make sure menu/Format/Word Wrap is ticked
- Search for the book title or author (ctrl-f for search)
- Now search backwards (tick UP in search bar) for 'de:cont' ~ the start of the area to delete
- Now search forwards (tick DOWN again) for 'de:cont' ~ the end of the area to delete
- That gives the two ends of the part you need to delete.
- Now use the mouse to highlight everything starting '<de:contentRecord>' and ending '</de:contentRecord>'; including both ends
- Hit the delete key
- And Save.