OK, i had the exact problem and here is what i did.
Went to:
https://www.pogo.com/account/my-account/lightreg2-recover.do
and i entered all the email addresses i had over the last few years until it eventually said "we have emailed you your details etc." Instead of "email not valid"
so at this point i knew i had the right address the game was once registered to.
i then went to this address as given tazmo8448
http://help.ea.com/en/contact-us/new/?product=battlefield-2142&platform=pc&subject=Unable+to+Log+On&category=download-installation-issues
I clicked on the live chat option, When i got through i just wrote the following.
Hi there,
I purchased a game (battlefield 2142) some time ago (about 5-6 years) when I set this game up I registered an account to my old email address I no longer have access to ([edit: email address removed])
I would either like to link this game to my current origin account, or pass the security hurdle so I am able to change the email address and gain access to this game as the CD key (26UW-PAUV-HKU4-UWPA-TRJR) is registered to the above mentioned email.
I would love to play this game again before all servers are shut down.
New email: [edit: email address removed]
Name: your name
Origin ID: your email
I was then asked one security question which was "what was your elementry school"
as soon as i said, i was given a link and a new product code, when i clicked the link, the game was added to my origin account and started downloading., no longer needed the CD. Now doing this to all my old battlefield games.
Best of Luck