HI all, I've upgraded to a new MBP Retina and have recently formatted my old MBP ready for sale. I don't have the original install disc but am connected to WiFi and can install the OS no problem. My question and concern is that it asked for my Apple User ID and password to pull down and install the OS. How will this impact me as I already have the same (latest) OS installed on my new machine? I.e. am I making a mistake by installing the OS on the old machine under my apple ID? What would you recommend in order to sell the machine with an OS on there? Thanks in advance for your help.