I have I tunes installed on my PC and have tried to copy my library on to my lap top. I did this by installing I tunes on the laptop and then copying each music file on to a flash disk and dragging the file into I tunes library screen on the laptop. All the song titles etc now appear on the library screen but when I try to play them I get an error message saying that the music file cannot be found. I know that I have probably done something stupid but what?