Hi guys, i got an intel based IMAC and its DVD drive is not working anymore. I need to reinstall the operating system, I've been trying with an external DVD drive (via USB), but when the installer ask me to restart the system to begin the process, it boots like there was restarting normally. I wonder if there is some kind of keyboard function or something that help me out to boot the Installation DVD from the external Drive (Sony external DVD). Every comment will be very helpful!!