How to find the id a ebook is registered to?

How can I find out which id I used to download a ebook to my pc. I tried every id I could think of and nothing works. Getting a message that the book is registered to a different id. I ied following some instructions found elsewhere on the web but think I messed things up. I can no longer open the ebooks I have in my Adobe Digital Edition.

Thanks in advance for your help.