HomerJ --> Okay. Now I just need a LiveCD.
GamingX --> I tried Root, root and admin. With and without passwords. Neither worked.
You could try
knoppix or if you are looking for something smaller, you could check out the
gentoo minimal CD. It is only 57.2 MB on x86 (likely the architecture you would be on an old PC). It has no GUI, however. If you have the install CD for the FC4 you have installed, you could probably use that as a liveCD (just exit to a rescue shell or whatever it offers).
Of course, FC4 is pretty old, you may just want to install the latest version. Otherwise you will be stuck with outdated software.
To find out the root user's name, you could run check in /etc/passwd. It will be the entry that says name:x:0:0. name will most likely be root, but I think some people change it.