Can't access book

I purchased an ebook a long time ago, and I have a new computer now, and I can't remember the password (or for sure the email) to authorize Digital Editions so it will let me read my book. On my old computer, I was authorized as one email and could read the book. On my Nook, I'm authorized as another email and can read the book. But I can't access either email to reset my password. How can I read my book on my new computer?