I was having an issue with a preupgrade of Fedora, somehow an old package that was no longer in use decided it was going to cause the installation to fail. After rebooting, finding the guilty package and removing it I started the upgrade again. This is where the error message “The root for the previously installed system was not found” occurred.
I did some research, tried mounting the file system then upgrading that way and still nothing.
According to this Fedora Forums post other people have experienced this issue. In cagonto1980′s post it explains the workaround:
Mount the filesystem, vi /mnt/sysimage/etc/fedora-release and change the release to the previous version. You may need to remember the version, mine was set to “Fedora 13 (Goddard)” and I changed it to “Fedora 12 (Constantine)”. After rebooting it started the upgrade. It appears the issue is Anaconda updates the release file and doesn’t change it back if the installation fails causing the next upgrade to think that the newest version is installed.
Thanks to cagonto1980 for the workaround.