Forgot your 'root' user password? Can't login to your system? There's still hope for ya. To gain access to your machine or to reset the lost 'root' password, depends on the boot loader on your machine.
If you have GRUB boot loader, select a boot entry and hit 'E' to edit. Then add '1' or 'single' to the end of the command. Hit enter to finish editing and 'B' to boot.
If you have LILO, type 'linux 1' or 'linux single' at the boot prompt.
If you need a password to access runlevel '1', add /init/bin/bash to the end of the command line.
This boots the system to a command prompt without startup scripts.
Manually mount '/' root file system as read/write:
mount -o remount,rw /
Once the systems is at the command prompt, edit /etc/shadow to remove encrypted password field. Normally second field of the first line.
After changes are saved, reboot system and use password command to create new password for root user.