Reset root password with GRUB
Boot machine into GRUB loader.
Highlight kernel you want to boot into.
Press (e) to edit boot process.
Add a space and append 'single' to the end of the boot sequence command line.
Press (b) to reboot machine.
Machine loads into root without a password.
Use passwd to create a new password.
Then issue 'shutdown -r now' to reboot machine.