Hi, I have a early 2011MBP that I'm giving to my son as I'm getting a new MBA (Yeah!). I plan on formatting the hard drive so he can start from scratch. I'm assuming the disks I have when I bought the machine are for Mountain Lion?.....I can't keep up with different ones but I've always upgraded each time a new osx has come out. So, when I format the drive do I have to reinstall each OSX in order? I hope this makes sense and sorry for being a rookie. Thanks for any input.