how can I authorize itunes songs purchased with ID that no longer exists?

Try this page and fill out the form at the bottom explaining your problem. http://www.apple.com/support/itunes/store/email/

MJ

I have exactly the same problem! When I try to play a song purchased under an old Apple ID (before I moved to Japan), I get: "This computer is not authorized to play "(song title)". Would you like to authorize it? To play this song you must authorize this computer to play songs purchased using the account "(my OLD Apple ID)". You may authorize up to 5 computers for each account."

I tried to authorize the song using my OLD Apple ID and password, but it didn't work because that Apple ID no longer exists. The weird thing is that after trying to authorize a song with my NEW Apple ID, the computer tells me I have successfully authorized it but then the song won't play and I get the same Authorize Computer dialogue box popping up again when I click the play button or double-click the song title.

It's VERY frustrating!

exact same problem, moved to japan, just had logic board replaced, now i can't log in with old .mac account to play songs previously purchased on itunes (although ironically I could log in here to leave this message). I get an unknown error (-50) message. just emailed itunes support, any tips would be greatly appreciated.
if you guys find a solution, please post.

ah, also.. using 10.4.8 and itunes 7.1.1