Authorize Computer (Again!) (and Again!)

Currently using Windows 10 on Dell Precision 7710

Always have used Dell laptops with Windows for iTunes since 2004

2004 installed iTunes and set account with (then current) aol email name for Apple ID. Around 2007 Opened a new account in my current email address, and authorised next Dell laptop using old AOL information/password. 2 laptops later, I forget the password, and talk with Apple support to get walked-through process to un-do accounts, and "Merge" them together. (Later learned this is impossible and didnt happen).. Next laptop, and at some point start getting messages that I need to "Authorise this computer" again with populated ID of the old AOL email..

Again talk to support, and get help to un link/ undo all accounts, and re-set accounts with a solution. ( I dont even remember what it was,, assumed it was "fixed" and moved on). Here I am again, at 4AM, trying to finish a presentation for work, and am getting these messages again on music I want to use..

Does anyone have a solution for me - to use 200 of the 300+ songs I have purchased and would like to play? Apple has informed me that there is no way to "merge all of my music onto one account,, and will have to live with this if it should ever happen again". Well it did. Any advice? I'm not super computer savvy, and as a Window user, Apple products really confound me. But I use iPhone, iPad, iPod and iTunes. Go figure.

I've tried to change user settings on my computer's control panel,, but even I know that is not really the issue.

thanks

Brad