Just on a cautionary note: do make sure the instructions you followed were
for your version of grub if you are still trying to resolve booting into the
64bit version. If you used version 9.1 or higher of Ubuntu, there is now
Grub2, which is different than the grub in the video I think. Try searching
for "fix grub2 after install" or "fix grub after install" for more info in
google. I havent had to do that yet, so I do not know the specifics or
which resource is the best, though I would think this is best done by
editing the grub config file then running "sudo update-grub".