In an attempt to see if I could remedy the "Error (null)" message I was getting from mai.app when trying to send e-mail, I installed Mac OS X on the same partition as Mac OS 9.1 (I did not delete the previous Mac OS X that I installed on a separate partition). The problem was not cured - I still received the "Error (null)" message. I now want to delete the Mac OS X on the same partition as Mac OS 9.1. I realize that Mac OS X creates some invisible files. I want to make sure that I do not delete files needed by the first copy of Mac OS X that I installed. Also, what is the best way to delete those invisible files? Must I acquire a copy of Ghost Hunter 2.1 or can I see and delete them by other means?