Downgrading GRUB [ Ubuntu 10.04 ]

Open a terminal:
Make backup copies of the main GRUB 2 folders & files. (Optional)

sudo cp /etc/default/grub /etc/default/grub.old
sudo cp -R /etc/grub.d /etc/grub.d.old
sudo cp -R /boot/grub /boot/grub.old

Remove GRUB 2

sudo apt-get purge grub2 grub-pc

The system will be unbootable until another bootloader is installed.
Once the packages are removed, many files will still remain in ‘/boot/grub’

Install GRUB 0.97

sudo apt-get install grub

With grub installed, the user must still create the menu.lst and stage1/stage2 files by running the following two commands.

sudo update-grub

Generates menu.lst ; Tab to “Yes” when prompted.

sudo grub-install /dev/sdX

Choose the correct device (sda, sdb, etc), normally the one on which Ubuntu is installed.

Creates the stage1 & stage2 files in /boot/grub and writes to the MBR.

Run this command to keep it from upgrading automatically:

echo "grub hold" | sudo dpkg --set-selections

Reboot           - Source: http://icewalkerz.blogspot.com