How to downgrade grub in ubuntu

The grub version 2 used in ubuntu 10.04 and later versions may be required to downgrade to grub 1.5 or legacy grub in some situations like we need to install the Ubuntu and other linux which uses the old grub like redhat linux 5 side by side.

To downgrade the grub, the following steps are recommended:
1. take a backup of the current /boot/grub folder:
#sudo mv /boot/grub/ /boot/grub_backup

2. Create a new /boot/grub directotry:
#sudo mkdir /boot/grub

3. Remove Startupmanager
#sudo apt-get --purge remove startupmanager

4. Remove Grub
# sudo apt-get --purge remove grub-pc grub-common

5. sudo apt-get update

6.Install Grub
sudo apt-get install grub
7. configure grub on harddisk sda
#sudo grub-install /dev/sda

8. open Grub configuration
# sudo Grub

in grub prompt:
find /boot/grub/stage1

root (hd0,2)

setup (hd0);

quit

9. install startup manager
sudo apt-get install startupmanager



10. reboot the system.