The start up disk pane in system prefs would not launch and holding down alt at startup kept rolling the imac. Booted up from OS9 CD. Used the Startup disk control panel that OSX installed in the MacOS9 folder and set the startup to MacOS9. On first boot disk first aid ran and "fixed a problem" as soon as it got into OS9 it froze. Powered of started up again, cancelled the disk first aid, it then booted up fine.