Why don't you see what's in that "Previous iTunes Library?" If their all duplicates, dump them.
I don't use iTunes more than once or twice a month, but I thought it had some kind of find and delete duplicates in one of it's menus. Have you looked at all those?
Or
Go back to your original thread and follow the instructions more thoroughly. With a detailed set of instructions it's all the more likely one will be missed.
A lot of that "nine page" document was for Windows users, just delete all that. Trim out the trivia and the "by the way, did you know" parts as well. Those instructions work, apparently, but the text is crammed full of not-needed-to-know info. Once you take the time to condense it to the bare minimum, you will have read it enough to understand exactly what do do and when to do it. What I'm suggesting is starting from scratch, attempting to solve a problem when there is no known cause is one of the hardest type to solve. Start from a known, good position and then work exactingly from there to the end. In the end, you will have a completed set up and probably faster than trying one and then another step, followed by yet another. That's my opinion, anyway. No need to mail the $ 0.000001372.