Install/Reinstall Grub2 on Ubuntu Lucid-Oneiric
Boot the Ubuntu Live CD (Try without installing).
From the Desktop, open a terminal – Applications, Accessories, Terminal.
Mount your system partition:
sudo mount /dev/sdXY /mnt
where X is the letter associated with the drive containing your system and y is the number of the partition containing your root directory.
Then reinstall GRUB 2:
sudo grub-install --root-directory=/mnt /dev/sdX
Note: Do NOT include the partition number. Instead use only the device on which Ubuntu was installed – sda, sdb, etc. Do not specify a partition number.
Unmount the partition:
sudo umount /dev/sdX