In essence – on a machine with iTunes, go to the iTunes store, login with your account (note, if you are using a friend’s computer be sure to log out of their account first), select the “view account” option, then there will be an option to “deauthorize all” – select this and ALL of your authorized computers will be deauthorized. Authorizing is simple. Go to Account > Authorizations > Deauthorize This Computer. By deauthorizing your computer, the access to your apps, music, TV shows, movies, books /pought on iBook Store/App Store/iTunes Store gets removed from that computer. Deauthorize Your Computer in iTunes Deauthorizing your computer means making it unable to access some contents you purchased from iTunes store such as songs, films, books amongst others. The specific operation is: - Open up iTunes on your Mac or personal computers; Now that you have understood the need of deauthorizing iTunes on your computer. Deauthorizing a computer is simple: Open iTunes on the computer you want to deauthorize. If your computer breaks down and you can’t deauthorize iTunes, you get rid of a computer before deauthorizing iTunes, or you upgrade your computer’s components, you may have wasted authorizations. But when you want to deauthorize computers, things can get a little more complex. Sign in with your Apple ID. Deauthorize a computer On a Mac, open the Music app, Apple TV app, or Apple Books app. To deauthorize your iTunes account in Mac or PC, you only need to choose the "Deauthorize" option on your computer, which could be finished in several seconds. Log in with your Apple ID if asked, then select Deauthorize. From the menu bar at the top of your computer screen, choose Account > Authorizations > Deauthorize This Computer. Remember that de-authorization does not mean that you would lose your files, you will only prevent the system from having access to such data. Choose Deauthorize. In order to play music, videos, and other content purchased from the iTunes Store, you need to authorize each computer you want to be able to play that content using your Apple ID. How to De-authorize Old or Dead Computer. On a PC, open iTunes for Windows.