You can now deauthorize all computers associated with an iTunes account (but you can only do that once/year). Here's how:
If you need to authorize your new computer and are unable due to already having five authorized computers, you can deauthorize all computers by doing the following:
- Click iTunes Store on the left side of iTunes.
- If you're not signed in to the store, click the Account button, then enter your account name and password.
- Click the Account button again (your Apple ID appears on the button), enter your password, and then click View Account.
- In the Account Information window, click Deauthorize All.
Note: You may only use this feature once per year. The Deauthorize All button will not appear if you have fewer than two authorized computers. If you need assistance on using this feature, please contact iTunes Store support via email (http://www.apple.com/support/itunes/store/).
- Open iTunes
- From the Store menu, choose Authorize This Computer. (In earlier versions of iTunes, access this option from the Advanced menu).
- When prompted, enter your Apple ID and password, then click Authorize.
PREVIOUS INFO 7/17/2011:
You must either deauthorize the computer before you no longer own it (or can't use it...) or wait until after you have 5 authorized computers assigned and then need to assign a new one.
Per iTunes support:
Authorize a computer to play iTunes Store purchases
To play many purchases from the iTunes Store, you must authorize your computer using your Apple ID and password. (Authorization helps protect the copyrights of the purchased items.)
You can have up to five authorized computers (Macintosh, Windows, or both) at a time. To play a purchased item on a sixth computer, you need to deauthorize another one. An iPod, iPhone, iPad, or Apple TV doesn’t count as a computer.
You can authorize or deauthorize a computer at any time. Be sure to deauthorize a computer before you sell it or give it away.
If you have trouble deauthorizing a computer, visit the iTunes Store Authorization FAQ website.
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