Thankfully, there are some useful tricks and tips on authorizing and deauthorizing iTunes on Mac and PC that you can find from the following article. In this case, for people who have multiple computers, it would be difficult in managing iTunes authorizations at the same time. In order to prevent unlicensed sharing in iTunes, Apple has added a licensing system with Digital Rights Management (DRM) requires users to authorize and play their purchased content on up to five computers at a time with their iTunes-linked Apple ID.
As a full-fledged marketplace for almost all kinds of digital entertainment, including music, movies, TV shows, applications, and books, iTunes has already grown into one of the most popular online media stores in the world.
