You can't read books that are DRM protected to one Adobe ID with a different ID, so you want to get your old ID working again.
Can you remember the email address you used for the initial authorization, and do you still have access to emails there?
If so, go to the page https://www.adobe.com/uk/account/sign-in.adobedotcom.html and click 'trouble signing in'.
If you don't, try online chat at http://www.adobe.com/support/chat/ivrchat.html and they may be able to help with a new password (not sure what their rules are).
Then unregister the Sony (ctrl-shift-E while it is connected to ADE), restart ADE, and reregister the Sony back to the original Adobe ID.