I have a laptop harddrive that I need replaced, and I have the new one waiting to be installed, but I want to make sure that I can still have the Mac OS on my system. I have the Snow Leopard UPGRADE DVD that came with my MBP. Does it make a difference if it says UPGRADE? Or is this all I need to boot it up? If so, I just insert the disc while it boots up and then hold the "C" key right?