Restoring GRUB in the MBR
Start up the system using the installation DVD (procedure tested with SuSE 10.0) in the rescue mode.
Login as root user.
Use
fdisk -l
to get the disk partitions and labels.
Then mount the "/boot" (or the "/" partition when there is no separate "/boot" partiton) on "/mnt". Finally use the "grub-install" command.
Assuming that /dev/sda is the device on which you want to update the MBR and that the partition /dev/sda5 contains the "/" partition:
mount /dev/sda5 /mnt grub-install --root-directory=/mnt /dev/sda