As root: (or prefix each command with sudo)

at boot: prompt, type knoppix 1
 
        mkdir /mnt/point
        mount -t <fstype> -orw /dev/blah /mnt/point
        mount --bind /dev /mnt/point/dev
        mount --bind /proc /mnt/point/proc
        chroot /mnt/point
        grub-install /dev/hdX (to install in MBR)