From Fedora Project Wiki

Boot from the Fedora install or live CD/DVD

Select "Rescue installed system"

Answer the prompts for language and keyboard.

Starting the network is optional and not needed.

Let the rescue mode mount your file systems in the read write mode.

Hit enter to get the root shell prompt.

	# chroot /mnt/sysimage (Change to your disk file system.)
	# vi /boot/grub/grub.conf (Editing boot loader configuration file)

Locate the password line and remove it (press dd on vi in command mode to delete a line)

Save the file then do:

       # sync ( changes are written to disk)
       # exit 

Congratulations! You now have now reset your boot loader password. The system will now unmount the file systems and reboot.

You can also use a bootable USB image for the same purpose. In case you do not have access to Fedora media, then also it is possible to reset the GRUB password. If you have Super Grub Disk, then boot your PC from that and install grub to the MBR. The password will be deleted automatically.

Another option is to boot from any Linux live CD/DVD (Knoppix, Parted Magic, System Rescue CD etc).

Mount the Fedora root partition (at say /media/sda1).

Open the file /boot/grub/grub.conf with an editor like gedit or kedit.

Delete the 'password ...' line and save file