Some iTunes help greatly appreciated.

I just purchased & received my new 27" iMac. Got it from the apple store, and got apple care too. Very pleased so far. Here the iTunes problem.

I moved all my music (about 70 gigs or so) from my old mac mini over to a Western Digital My Passport (brand new 1 TB version). Worked great. But I forgot to 'de-authorize' my old mac mini for iTunes. I still haven't done that yet, though I did save the old mac mini.

When, when I fired up my new iMac, I had problems opening iTunes. Bear in mind my friend and I hadn't figured out yet that the failure to de-authorize the old mac may have been the reason we were having trouble getting iTunes to work on the new iMac. So we probably did some stupid stuff, trying to copy files and trying to get the new iMac authorized. So bottom line is I have two or three folders that say iTunes library. I only want one. And I want to be able to find it! And I want it to work properly.

Eventually I was able to get some stuff going. The problem is, I now have different versions (i.e., apparently some authorized & some perhaps not authorized) on my new iMac.

I have an iTunes account under a very old hotmail email address. I have an apple login from a newer gmail account. I've read some stuff on this and apparently apple is now very picky about what you can have for iTunes accounts. I want to just take everything from my Passport and get it authorized for this iMac. And then remove all the other lousy iTunes stuff that I have on my new computer. Without messing with any security stuff that might either a) cause me to not be able to authorize my iTunes account or b) lose any of my music. Ideally I'd love to start anew and create a brand new iTunes account, using my newest (gmail) email address. But I've heard and read that it could cause some problems and I certainly don't want to cause any more! I'm afraid of doing anything that might mess this up further.

I know, first world problems, right? By the way, I like the new iMac very much.

Any suggestions from folks who might have some good experience are much appreciated. Thanks!