Ext. HD for IIgs and Mac

[joseph.m.barbey@uwrf.edu (Joe Barbey)]

I just bought an externall harddrive, and I'm trying to set it up as one
HFS partition.  I would like to be able to use it on both my GS nad my
roommate's Mac.  Unfortunately, when I go in to the Advanced Disk Utils on
the GS, and try and partition it, it comes back with 

        Unable to load the Macintosh driver. HFS partitions
             will not be usable on Macintosh computers.

Does anyone have any idea where the 'driver' I need is?  Also, I tried
running the Apple HD SC program from ftp.apple.com on his Mac, but that
didn't even see the drive.  I have the 6.0.1 disks, but don't have any
idea of what to look for.  I tried loading the HFS FST, and that didn't
help, either.  

Any help would be greatly appreciated.

-- 
Joe Barbey
UW - River Falls
joseph.m.barbey@uwrf.edu