I just bought a new Macbook air and when I set it up I used my GF apple ID as i did not have one. After trying to changing it us user setting with mine it won't allow me to update any software unless I use my GF apple ID. I called apple and they told me that the ID you put in at the installation will be with the computer for ever. you can't change it. Now this is not a big problem for me but what happens to people that want to sell their MacBooks? you would have to sell your ID as well? Any idea?