well, it should be pretty clear what to do, pop the fedora core cd in, and go through the steps until you get to wipe the partition table, and do so. then you can, instead of re-formatting in any filesystem, just turn off the computer, making sure you save the changes, otherwise, it won't do anything. then, put your newer cd in, and you should be good to go. the setup will prompt you to format the drive and everything.