Buffalo HD-PHS series Quick Setup Manual page 8

Macintosh Setup
Mac OS 9
In Mac OS 9, the MiniStation will automatically mount on the desktop.
The MiniStation comes pre-formatted with Windows FAT32. Your Macintosh will
recognize this format so you may begin using it immediately. This format will allow for
use on both Macintosh and Windows computers.
Mac OS 9 will not allow you to reformat the drive to a Macintosh format.
You must use Mac OS X or a third party disk utility to reformat the drive, if reformatting
is necessary.