I'd boot up in rescue mode, then edit the /etc/passwd and/or the /etc/shadow file and remove the password for root, reboot, and hope it all works.
Plop in your install CD, and choose rescue mode (or somehow get to a command prompt from your install CD). Then, mount up your root filesystem ( / ) somewhere easy, something like:
mount /dev/hda1 /mnt/stuff
Assuming /dev/hda1 is the partition containing your root filesystem (which should contain /etc ). Then, using a command line text editor, edit the files mentioned above, and remove the following:
Remove that "x"
Then in /etc/shadow:
Remove those wierd characters (the TYe70...), save and exit. Now reboot, and hope it all worked