Ubuntu :: Chroot Then "update-grub" Gives Errors

Ok so I have a USB external hard drive with Ubuntu 10.04 LTS on it but I did something to ruin it's grub or something. So what I did to make my USB HDD bootable again is:

Code:
sudo mkdir -p /mnt/chroot
sudo mount /dev/sdc1 /mnt/chroot
sudo mkdir -p /mnt/dev
sudo mount --bind /dev /mnt/dev
sudo mkdir -p /mnt/proc

[Code]...

I don't know what to do about that error. It took me a while to understand how to learn chroot and thanks to some ..... videos I finally learned how and then it felt like a climax when I was about to issue the update-grub command and then when it didn't work, I felt bad lol .