Deauthorising a computer i sold!
I have sold my computer before deauthorizing and I am 5 months away from deauthorising all - HELP>>
OS X Mountain Lion (10.8.4)
There's nothing you can do except wait the five months. However you should change the password on the Apple ID you use to log into iTunes to prevent the new owner from purchasing anything.
You can do this at http://appleid.apple.com . If this is also your iCloud login you will need to log out of iCloud on all your devices and log back in again.