Assumptions :
1. You had a Linux partition
2. For some reason you re-installed windows and now cant boot into Linux
3. You cant boot into linux even if you select the specific HDD in BIOS boot options
You will need :
1 Either a USB boot version of ubuntu or Live CD you can boot with
To create USB Memory Boot Stick :
A. Download your ubuntu .iso file
B. if you are on windows install LiLi from here http://www.linuxliveusb.com/ and create the boot USB drive.
To restore Boot :
1. Boot From you USB stick.
2. Now we will have to mount the local drives.
3. Find out from fdisk or parted the parition where Linux is located.
4. Mount the ubuntu partition drive
sudo mount /dev/sdXX /mnt (example 'sudo mount /dev/sda1 /mnt')
5.Only if you have a separate boot partition:
sudo mount /dev/sdYY /mnt/boot.
6. Mount the virtual filesystems:
sudo mount --bind /dev /mnt/dev sudo mount --bind /proc /mnt/proc sudo mount --bind /sys /mnt/sys
7. To ensure that only the grub utilities from the LiveCD get executed, mount /usr
sudo mount --bind /usr/ /mnt/usr sudo chroot /mnt
8. If there is no /boot/grub/grub.cfg or it’s not correct, create one using
update-grub or update-grub2
9.Now reinstall Grub
grub-install /dev/sdX (e.g. grub-install /dev/sda. Do not specify the partition number.
10. Verify the install
sudo grub-install --recheck /dev/sdX
11. Exit chroot : CTRL-D on keyboard.
12. Unmount virtual filesystems:
sudo umount /mnt/dev sudo umount /mnt/proc sudo umount /mnt/sys
If you mounted a separate /boot partition:
sudo umount /mnt/boot
13. Unmount the LiveCD’s /usr directory:
sudo umount /mnt/usr
14. Unmount last device:
sudo umount /mnt
15. Reboot.
sudo reboot.
abridged from
http://opensource-sidh.blogspot.com/2011/06/recover-grub-live-ubuntu-cd-pendrive.html