I would mount the root / & then mount the /etc in the /.
Assuming /dev/hda7 is your root and /dev/hda6 is /etc.
Boot knoppix.

become root user in knoppix.
su -

Then mount the /root, but first create a mount point.
mkdir /mnt/suse-root
mount -t reiserfs /dev/hda7 /mnt/suse-root
mount -t reiserfs /dev/hda6 /mnt/suse-root/etc

Then chroot into that environment
chroot /mnt/suse-root /bin/bash

Then change the password.
passwd

Then exit
exit

Then unmount the partitions
umount /mnt/suse-root/etc /mnt/suse-root

Then reboot
init 6

The above steps have always worked for me.