Go in System Preferences->Startup Disk
If OS 9 is installed, you should be able to select it and restart on OS 9. Btw you know you can use Classic under OS 9 to run old apps? why do you want to boot under OS 9?
btw, if you post on this forum, you can at least go back and check your post. And other persons might be interested in the answer, so don't expect people to email you directly. (you will probably receive an email notification though).