Q: Is there a way to play purchased iTunes music on iTunes (8.1.1) on a non-networked computer? That is, a computer that cannot connect to the iTunes Store?
A: You can play protected iTunes Store tracks on a computer without being connected to the Internet as long as the computer has been previously authorized for your iTunes Store account.
Unfortunately, authorizing the computer with the iTunes Store requires an Internet connection in the first place so that your computer can contact the iTunes Store and download the necessary authorization information. This information is computer-specific and cannot be transferred from another computer. You can manually authorize a computer simply by selecting Store, Authorize Computer from the iTunes menu.
Once authorized, however, your computer does not require a connection to the iTunes Store to actually play back your purchased content—it relies on the local authorization information only. You could therefore connect your computer to the Internet, authorize it for your iTunes Store account, and then disconnect it and continue to play your purchased content without having to go back online.
Note that if you’re working with “iTunes Plus” tracks, these do not include any type of copy protection and your computer does not need to be authorized in order to play them. All new music tracks purchased from the iTunes Store should now be in the iTunes Plus format.