I have an HP 630, and would like to install Ubuntu. All goes well until the point where you have to choose how you want Ubuntu installed. I choose on the whole HDD, I want Windows off the HDD. I press enter and about 5 seconds later the CD tray open and the computer reboots. This happens over and over. How do I format this Window HDD completely to install Ubuntu 13.04. I have tried 3 different CD's and the same thing happens each time.