ah... stupid question: how do you "deauthorize" a computer in iTunes?

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Thanks, I also found it online:

"How do I deauthorize all of my computers?
If you have authorized five computers, a button labeled "Deauthorize All" will appear in your Account Information screen. This button will deauthorize all computers associated with your account. You can then reauthorize up to 5 computers. Note: You can only use this feature once a year."