Good URL: http://www.ioncannon.net/linux/68/upgrading-from-fc6-to-fedora7-with-yum/

Install the fedora release Fedora 7 RPMs:

rpm -Uhv http://download.fedora.redhat.com/pub/fedora/linux/releases/7/Fedora/x86_64/os/Fedora/fedora-release-7-3.noarch.rpm http://download.fedora.redhat.com/pub/fedora/linux/releases/7/Fedora/x86_64/os/Fedora/fedora-release-notes-7.0.0-1.noarch.rpm

Set /etc/yum.conf file:

[base]
name=Fedora Core $releasever – $basearch – Base
#baseurl=http://www.mirrorservice.org/sites/fedora.redhat.com/core/$releasever/i386/os
baseurl=http://www.mirrorservice.org/sites/fedora.redhat.com/releases/$releasever/Fedora/i386/os/

[updates-released]
name=Fedora Core $releasever – $basearch – Released Updates
#baseurl=http://www.mirrorservice.org/sites/fedora.redhat.com/core/updates/$releasever/i386
baseurl=http://www.mirrorservice.org/sites/fedora.redhat.com/updates/$releasever/i386/

Run following commands:

[root@server ~]# rpm -e authconfig firstboot-tui-1.4.23-1.noarch authconfig-gtk-5.3.18-0.1.fc6.i386
[root@server ~]# yum -y update

Then, to upgrade to Fedora 8:

rpm -Uvh http://www.mirrorservice.org/sites/fedora.redhat.com/updates/8/i386/fedora-release-8-5.noarch.rpm http://www.mirrorservice.org/sites/fedora.redhat.com/updates/8/i386/fedora-release-notes-8.0.1-1.noarch.rpm

yum clean all

yum -y update

Edit: Then to Fedora 9

rpm -Uvh http://www.mirrorservice.org/sites/download.fedora.redhat.com/pub/fedora/linux/releases/9/Fedora/i386/os/Packages/fedora-release-9-2.noarch.rpm http://www.mirrorservice.org/sites/download.fedora.redhat.com/pub/fedora/linux/releases/9/Fedora/i386/os/Packages/fedora-release-notes-9.0.0-1.noarch.rpm

yum clean all

# Note: may need to remove some packages that conflict.

yum -y upgrade