From Fedora Project Wiki
How to Reset Boot-loader Password
This document provides a method for resetting boot-loader (GRUB) password in Fedora.
* Boot from Fedora CD or DVD (or any other Linux Live or Rescue CD). * * * Open a Terminal (or Konsole or a Shell)
#mkdir /media/abc #mount -t ext3 /dev/sda2 /media/abc
* Open the file /media/abc/grub/grub.conf in a text editor like 'gedit' or 'kate' * Delete the line that goes like 'password -md5 blah...blah' * Save file