If your start out at the console screen, then enter root as the user, and enter the root password. If starting out in KDE, GNOME or other X-Windows environment, It is best to log in as a user and use the ´su´ command.
Another way to work as root is to init into a different run level such as ¨init 1¨ however, you need to be logged into root to do this. In an emergency, booting with a rescue disk, or the first install disk (and typing in <F1> then ¨rescue¨) will allow you to perform some of the root functions if you are unable to boot into linux.
Once you log into root, I would suggest making a rescue disk if you don´t have one. If it will fit on a floppy, then the command is mkrescue. If it is too large to fit on a floppy, then mkrescue --iso will produce a rescue.iso file that you can write to disk.