I have purchased a book from borders and downloaded the Borders Adobe digital editions SW the book is in a borders application on my Mac. I have opened Digital editions and expected it to find the book and install it so I can transfer it to my Nook. Nothing happened. I can read the book by opening it in Borders app and read it there but I want to read it on my Nook
Do you know where the epub file is located on your computer? Sometimes you have to "add" it to your ADE library manually. Ctrl+O will open a file manager window. Look for the book there and see if it will open in ADE.
Then you should be able to drag it to your reader if your reader appears in the reading list. If there is security encryption you may have a problem copying the book into different readers, and I can't help you there. There are some online message boards where they try to explain how to get rid of the encryption, but it is SO Greek to me.