I am considering installing an additional hard drive in my Mac 7600. I am confused about the various configurations in SCSI drives I see advertised, such as I, II or III, ultra SCSI and wide SCSI. Can you explain the differences and what is involved in installing them? Also, does a drive have to be advertised as Mac compatible or like a floppy can any drive be formatted for the Mac? I have seen some good prices at auctions but am reluctant to bid since I don’t know whether they will work in my machine.