I've just started getting a message box when I try to play a song in my music library on itunes. It says "The song (whatever the songs name is...it's doing it to all of my songs in the library) could not be used because the original file could not be found. Would you like to locate it?". If I say yes it takes me through a sequence of files to chose from to open. And when I get to the itunes music folder it show some of the songs I have on itunes but not nearly all of them. What could be causing this message to appear and how can I eliminate the problem? I've never used any other music file manager. I'm using the latest version of itunes and have been for some time without problems.