How many computers are authorized to play music from my account?

To see how many computers are currently authorized to play music purchased with your iTunes Store account:

1. Open iTunes.
2. Click iTunes Store in the Source list.
3. If you're not signed in to the store, click the Account button and enter your Apple ID and password.

   

    

4. When the iTunes Store opens, click the Account button (your Apple ID appears on the button), enter your password, then click View Account.

   

   

The Apple Account Information page that appears shows you how many computers are currently authorized.

Do you think you have used up multiple authorizations with one computer? Try this:
One computer using multiple iTunes Store authorizations.