Q: I moved iTunes to an external hard drive. When I click to check for updates, I have to close iTunes. Then it downloads to my Mac hard drive and not the external. How to I update the copy of iTunes on my external hard drive?
A: You don’t actually need to keep your iTunes application on your external hard drive—you can easily have your iTunes library database and your media content stored there and leave the application on your Mac’s internal hard drive. In fact, it’s best to keep all of your applications in the Mac OS X “Applications” folder as that’s where programs like Software Update expect to find them.
Our guide on Transferring your iTunes Library describes the different aspects of iTunes: the application, the library database, and the actual content, and describes how to transfer the library database and the content onto an external hard drive. There is no connection between the location of the iTunes database and content and the iTunes application, however, so there’s not really any point in keeping the iTunes application on an external hard drive, particularly since every Mac comes with iTunes already installed on its internal hard drive.