Updated console, now locked out of gamertag because I don't know 15 year old password.

Hello, first it's a pleasure to be able to help you today.

My name is welcome to the community.

Hello Brittni, try to reset your password on the PC by the link below, if it does not allow the system sends you a code for your security information, be it email or phone but you do not have them or have changed them, choose the option "I have none" you will be able to add a new security information but the account will enter a 30-day quarantine.

You can go to this link to reset your password:

https://account.live.com/password/reset

You can also check this link as an additional guide:

https://support.xbox.com/en-US/help/account-pro...

I set up my microsoft / xbox account years ago under another email. I do not know that password and can't recover it because I don't have access to the email. Now, I am locked out completely, as the passkey was entered wrong 3x by my son, and it is prompting
me to put in my password for the email I used initially to set it up. I don't have this.

No, sorry if there's a misunderstanding.

What i wish to do is to transfer my old Gamertag ( 4+ year old account) to a new WLID account that i created. I can still log into Xbox live from the Xbox console, however the system asks me to log in my old WLID password before i can make the WLID change,
but i can't since the account is locked.

The reason my old WLID got blocked was because apparently someone tried to log in too many times using a wrong password.

yes the email isnt working because its like a year old and i stopped using it and now i cant get to xbox live to change it because the update wants the old ones password

The Account Recovery form is the only way to recover an account you cannot access for whatever reason.