Imagine you spend an entire week painfully setting up your computer to dual boot with XP and Ubuntu (Breezy) using GRUB and have configured Ubuntu to the max and you have to reinstall XP. No more GRUB, XP has overwritten the MBR!!!

This happend to me and I was frustrated, but I was able to google it and got GRUB installed back on the MBR and was able to boot into Ubuntu again.

Here is how you can do it.

1. Insert the install cd/dvd in the drive and boot from it.
2. Proceed without changing any setting until the point where you are asked to partition the disk(s).
3. Select the option to partition the disks manually.
4. Load the partitions (/, /boot, /root, et. all). The partitions have to be loaded in the same manner as you had when the system was up and running properly. Save changes to the disk.
5. Now you will get an error message saying that you are about install on an unclean partition. Ignore this warning and proceed untill the GRUB installation page.
6. You can also cancel this operation and go to the installation’s Main menu and directly jump to Install GRUB section.
7. Install the GRUB on MBR if all your operating systems are listed.
8. Remove the install media from the drive and reboot.
9. You’ll find the GRUB menu when you reboot.

Cheers n Enjoy!!!
DeeJay