Originally Posted by dreams
Like Charlie said, contact customer service. They were able to combine my old account and password to the new linked amazon account for me. They are now all under one amazon account. I don't remember exactly how it worked, but I may have had to redownload some of them.
I just called Audible CS, and sure enough, this is a new feature...I've been trying to get my libraries consolidated for a long time!
No need to call CS as it turns out, if you know your old account credentials.
You just log in to the non-amazon account, go to Account Details, and under Account Settings, click the "NEW--use amazon account" link and enter your amazon info. Both my libraries were instantly merged into my amazon account.