I've got a PC which two operating systems: Windows (XP) and Ubuntu (10.04). I had wisely installed Windows at first and after that Ubuntu, having read about Windows being more rude than Ubuntu when it comes to overwriting the master boot record.
Recently I reinstalled Windows. After rebooting, of course, Windows' boot loader had defeated Ubuntu's with the result that I couldn't see my Ubuntu during boot and thus couldn't start Ubuntu any longer...
I found a great help article about just that thing on:
The central steps which helped me out were:
- Booting an Ubuntu Live CD
- Mounting the old Ubuntu partition by clicking on the drive in the Places menu
- Console command: sudo grub-install --root-directory=/media/0d104aff-ec8c-44c8-b811-92b993823444 /dev/sda
- Be sure to previously find out the device name of the disc with Ubuntu on it as well as this long number (which can be found out by the mount command)