You must use the "SystemDisk" utility (found in the "macOS9" folder on the OSX disk) to select an OS X startup disk from OS 9. When using this utility, try selecting a disk by option-double-clicking it. You will see the boot options for that device. If you edit these options and save them, they will be saved to a device called 'custom setup' -*don't* do that! Doing so caused my Powerbook 2000 to not be able to find *any* startup disk. I had to boot from a CD and use Apple Drive Setup to replace the disk driver!