Adding Distro to Grub

I am having some difficulty adding a 2nd Linux (Slackware) to grub in SuSE 9.0 It is on hda4 and using Yast2 should I be able to mount it as / ? but it seems I can't because SuSe is already /. How can I get hda4 (Linux Native) to be mounted and show up at boot. Thanks