It won't let you install OS9 now as a newer OS is already there (OSX), at least I believe this to be true. Open up your software restore disk (comes with you mac). Somewhere in there is an image(s) of a full OS9 install. Copy the data from this disk image to a new folder on your HD called OS9 or the like. Then update to the newest version of OS9. Ask someone else for the folder the image is in I don't remember. I abandoned that piece of sh1t OS9 years ago.