I have dual boot pc with XP and Redhat 7.5, I want to upgrade the Redhat to the latest version of Fedora. So I down loaded three files, yarrow-x86_64-disc1.iso, disc2, & disc3, and burn them to CDs, but I could not boot from disk1. What step or steps am I missing in creating these CDs that is stopping me from making them bootable?