1.

Add a Protected AAC File to iTunes

On a computer other than the one where a protected AAC file was purchased and downloaded, add a copy of a protected AAC file to your iTunes Library as described in 11 Add a Music File to Your iTunes Library . This file might be copied to your computer over the network or sent as an email attachment, or it might be a song in a shared iTunes Library to which you connect as described in 59 Listen to Shared Music on the Local Network . Regardless of how you got access to the file, the DRM restrictions on it ensure that you cannot open the file without proper authorization.

23. Authorize a Computer to Play Purchased Music

2.

Attempt to Play the File

Select the protected AAC song and click the Play button. The song doesn't begin playing; instead, a dialog box similar to the Sign In window in the iTunes Music Store appears. The Apple ID for the account used to download the track is already filled in, and you must enter the password for the account, proving that you're the person who purchased the music (or someone to whom the purchaser has given access privileges), to proceed.

3.

Sign In to Your iTunes Music Store Account

When you enter your password and click Authorize , iTunes connects to the central authorization server and checks your credentials. It also makes sure that one of the five authorization slots for your account is available; if so, you get a message saying that the current computer has been successfully authorized, and the song begins to play.

From this point forward, you won't need to authorize to play any other protected AAC files on that same computer, provided those files were all purchased with the same account. iTunes keeps track of whether it has been authorized for a certain Apple ID; if you have a catastrophic failure such that you need to reinstall your operating system or rebuild your computer from scratch, you have only to perform the steps in this task again to reestablish the authorization for your computer (it doesn't use up another authorization slot to re-authorize a computer that the iTunes' servers already know about). However, you should deauthorize your computer before you sell it, or if you need to send it in for service; deauthorizing prevents potential situations in which a single computer might be assigned multiple, redundant authorizations.

NOTE

You can have more than one Apple ID authorized on a single computerfor example, if two people share a computer but use separate music-buying accounts. Even having two authorization slots mistakenly used by a computer is not in itself a problemit just means that one of your five authorization slots is being wasted . Deauthorizing a computer multiple times until it's no longer possible to do so is one way to clear up this problem.

4.

Authorize to Play a Protected File in the Finder (Mac only)

In Mac OS X, you can play protected AAC files in the Finder, by previewing them in Column view or by using the Preview pane in the Info window (available by selecting the file and choosing File, Get Info ). Because the authorization process is handled ultimately by QuickTime, which is built into the Finder, attempting to play a protected AAC file in the Finder on a computer that isn't authorized results in the same dialog box appearing as in Step 2. Enter your password for the Apple ID and click Authorize to play the AAC file and any others purchased with the same account.

5.

Deauthorize a Computer

If you want to revoke the authorization for a computer to play your purchased musicfor example, if you want to authorize an additional computer to play your music, and your five authorization slots are all used upyou can do so. Choose Advanced, Deauthorize Computer from the menu bar in iTunes. You are prompted to enter your account password; type it in and click Deauthorize . iTunes makes the necessary transaction with the Apple servers, and a message tells you that the computer has been successfully deauthorized.

It's a very good idea to deauthorize your computer before you sell it or send it in for service to avoid confusing the server into assigning more than one authorization to your computer. If you suspect that this has happened , view the related documents at the iTunes and Music Store Service and Support (Mac) or Music Store Customer Service (Windows) web links available under the Help menu in the iTunes menu bar.

NOTE

Deauthorization requires your password as a security measure. You wouldn't want just anybody to be able to come along and revoke your computer's ability to play your own files, would you?

6.

Check Authorizations for Your Account

If you're not sure how many authorizations your account is using, you can check this information using the account information page in the iTunes Music Store . Click your Apple ID in the Account box, enter your Apple ID and password in the dialog box that appears, and click the View Account button. The screen that appears shows you how many computers are authorized to play music for your account. Compare this number against the number of computers you know to be authorized for your music. If there's a discrepancy, contact the iTunes Music Store support staffchoose iTunes Music Store Service and Support (Mac) or Music Store Customer Service (Windows) web links available under the Help menuto have the support staff revoke incorrect authorizations and free up those slots.