rescue grub

What to do when you screw up your MBR.
The following are the steps you should follow;

Run rescue CD, in rescue mode:


mkdir /mnt/j

mount /dev/sda3 /mnt/j

mount -t proc none /mnt/j/proc

mount -o bind /dev/ /mnt/j/dev

chroot /mnt/j /bin/bash

In new root:
grub> find /boot/grub/grub.conf
(hd0, 2)

grub> root (hd0,2)

grub> setup (hd0)

grub> quit

sync and reboot