iTunes allows your to authorize up to 5 computers at a time to be used with an iTunes account. When you deauthorize a computer, you remove its access to certain content that you bought from the iTunes Store, iBooks Store, or App Store, such as music, movies, TV shows, apps, and books. You won’t lose your content, and nothing will be deleted from the computer. When you deauthorize a computer, you only prevent it from accessing protected content. You should deauthorize your Mac or PC before you sell it, give it away, send it in for service, or make major hardware upgrades.
1. Open iTunes.
2. From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account > Authorizations > Deauthorize This Computer.
3. When prompted, enter your Apple ID and password.
4. Click Deauthorize.