1) Boot from a Live CD
2) Open a terminal window or switch to a TTY and enter:
sudo grub3) At the grub prompt, use the following command to determine where grub is installed:
find /boot/grub/stage14) Using the hard disk and partition given by the above, enter:
root (hd0,6) setup (hd0)5) Then quit grub by typing quit, and reboot your machine.
If you need more information about the partitions on your disk, use:
sudo fdisk -lNote that the partition numbers shown by fdisk begin at zero; grub however uses a zero-based index, so you'll need to subtract one from the number given by fdisk.