mv '/System/Library/CoreServices/Classic Startup.app'[space][Replace [space] with an actual space character, and enter as one command].
'/path/to/new/location/Classic Startup.app'
Paul C. had another idea which may also work, and would put a dialog onscreen each time Classic tried to launch:
You should be able to do this by removing "Classic Support" and "Classic Support UI" from the 9.1 System Folder. You'll get asked when Classic is about to start whether you want to install certain items that Classic needs; I think if you answer "no", then Classic won't start up.Either of these methods should prevent Classic from launching.

