I have recently upgraded my macbookpro. I had accumulated a lot of rubbish on my old machine and it had started to play up so I didn’t use migration assistant, I just started again from scratch, installing the programmes I needed. So that I didn’t have any potential issues with registration keys I created the same username on the new machine as the old machine. I have a rather large iTunes library (~300GB of music, videos, books and apps) with playcounts and ratings...