I just got a used iMac and it had Snow Leopard disks. I don´t want to install Mavericks, I need to install Mountain Lion. How can I do that? Can I get the mountain Lion from the App Store? Or is only the newest Mavericks available there? Or do I need the Mountain Lion disks? Are there Mountain Lion disks even in existence? Does Apple sell them? How will I get the latest Mountain Lion updates? Confused!