new install, new apple id, new email, can't play some songs

Had my old apple ID back in the pre mobil me days, went through iWeb, MobileMe, Mac.com, through each change until iCloud.

Been using my iCloud ID, which I think I established in 2008 possibly through .mac that was then upgraded/morphed into iCloud whenever.

Here's my delimma:

had to do a full erase and install on my old computer for the first time in ... well, I think since I started with mac computers in 2003. Sure has caused some problems.

iTunes is asking me to authorize my "new" computer to play with the current library. I have forgotten all about the old email address, which I used before dot mac and my conversion to dot mac (and through to today). Turns out, a fair amount of the songs I purchased were under a generic ISP email address which I haven't used since 2008, I'm thinking. But it hasn't been a problem until I erased and restarted with a clean install.

Now it wants me to reauthorize my computer to play the songs from the very old email account, which was my apple id back then. I haven't had that email address since dirt was young. Wouldn't even begin to know what password I used or how to reauthorize my account.

What am I to do so I can play these songs? Still me, same owner, just a new day.

Is there a way to transition my original old apple ID to merge with my current one?

How can I reestablish permission to play when that email account hasn't worked in years and I wouldn't even begin to know passwords, how to authorize it, can't access the email to do the forgot password deal, and so forth.

Any suggestions?

Thanks!