To insert the boot option for the old installation start with
Code:
su
mcedit /boot/grub/menu.lst
and insert this three lines

title KNOPPIX old installation
root (hd1,0)
kernel /boot/vmlinuz root=/dev/sdb1 (.. and rest of this line)

Save with F2 and quit mcedit with F10. By the way "lang=" has no language declaration.