This is confusing. My 13 inch aluminum macbook comes with a CD called Mac OS X Install and Applications Install DVD. Aren't these things already on my computer? Do I have to install them or not? Also, I have iWork but I've already installed it on one computer. However, I had to return that one after a few days because the computer dude said the hard-drive was shot. Will iWork install a second time on a new computer? THANKS!!