After you have used up all five Authorizations, you can deauthorize all.computer and then authorize the one you want. You can only do it once a year.
For repeat authorization see:
Have no fear, these are music and videos I've had on my iPod Touch for years. They are all properly coded. The music is MP3s and the videos are quicktime. I have never had any problems with them. They all play fine. The files are all located on a secondary hard drive.
It is iTunes that is causing the headache. It won't let me synch globally. I have to import the movies separately, and the music separately. I keep getting messages that I am not authorized to synch, but when I go to authorize, I get another message telling me that my computer is already authorized.
Anyhow, I have been able to get everything back on my iPod, so all is good for now ... until I try to add something new.
Btw, I never have any of these problems with my Android devices (tablet and phone) -- it's just drag and drop. I wish Apple didn't have to be so controlling.