[mikester]

iTunes accounts can only be registered with 5 computers at a time. It's part of their Digital Rights Management (DRM).

What is means is that if you have a given iTunes download you can only load it on 5 devices. Devices can be computers or iPods, for example - say I download "Hot for teacher" on my own computer. I can then send that file to my wife's computer and when she tries to play it in itunes it will prompt her for *MY* iTunes account password. I can allow her to listen to my downloaded music by putting my iTunes user/pass into the prompt and then she will be able to play it. Apple DRM allows 5 such instances; once you log in to another "session" of DRM to log out in iTunes click advanced in the menu bar and then "deauthorize this computer." That'll free up a session; if you want to deauthorize all (say there are some stray ones out there or something) go to the apple store in iTunes and then click on your username up in the right hand of the menu bar. It should prompt you for your user/pass and then give you your account info including how many sessions you have active. If it is 5 it should let you deauthorize all.