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I found out how to deauthorize all machines - just reach the limit, and an option appears.

How can I deauthorize selected machines?

http://www.tuaw.com/2006/02/20/deauthorize-all-itunes-machines-at-once/

Suggestions welcome. :D

To deauthorize a computer

Open iTunes.
From the Store menu, choose Deauthorize Computer (In earlier versions of iTunes access this from the Advanced menu).
Select "Deauthorize Computer for Apple Account" and enter your Apple ID and password.
 
Now, I messed up. I gave my mother my old powerbook as a birthday present, but I forgot to deauthorize the computer before reformatting it for her. Is there a way to do it say my the iTMS?
 
Now, I messed up. I gave my mother my old powerbook as a birthday present, but I forgot to deauthorize the computer before reformatting it for her. Is there a way to do it say my the iTMS?

The only way to remote deauthorize is to get your total number of authorizations up to 5 then use the deauthorize all option.
 
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