I have a MacBook Pro 2009. I installed Snow Leopard on it and wanted to upgrade to the next OS. I have the factory disc for Lion, but every time I click the install and the computer needs to restart from the disc, the screen remains blank white and the apple logo will not appear. It's like the screen freezes. I hear the disc inside whirling around for a minute and then quit. I eventually have to reboot and eject the disc so the mac can start back up. What am I doing wrong?