[dagaz]

What version of OSX are you using?

Try holding down the apple and s keys together straight after the startup chime. When you get to a command line prompt type "fsck -y" (or "fsck -yf if using 10.3). If you get the message **FILE SYSTEM WAS MODIFIED** keep typing the fsck command until it tells you everything appears OK. Type reboot. Hopefully this will boot you into OSX. From there go Apple > System Preferences > Startup Disk and select your OS9 system folder to boot back into OS9.

NB: The option key will only let you choose your startup system when they are installed on different drives or partitions.