I've been searching for a solution to this and think I found it here->
http://www.supergrubdisk.org/wiki/Multi_Distribution_Boot_Howto
which states:
'''''''''''''''''''''''''''
You will have to open a Grub terminal and run:
grub> device (hd0) /dev/sda
grub> root (hd0,1)
grub> setup (hd0,1)
grub> root (hd0,2)
grub> setup (hd0,2)
and so on.
grub> quit
sync
''''''''''''''''''''''''''
And then I suppose that's it.
Does this look right?

-- 
:-)~MIKE~(-: