The way ADE works, it links the ebooks to the computer and to the ID you
used when you downloaded them. You cannot use the second ID and get at
those ebooks downloaded with the first ID.
You can deauthorize your computer under your second ID and then reauthorize
it under your first ID, but if the ebooks had to be reloaded to your
computer, this might not work. If they're library ebooks, I'd wait until
the loan period expired, delete the ebook from the ADE library using your
computer's utility programs (since you can't use it anyway), and then check
out the ebook with your new ID. I know that process works.