Have you got QuickTime 2.5 installed? It supports Component Manager which you might be missing.
For your config, do not go to System 7.5.5. If you can't get 7.0.x running, recreate your system using 7.1 plus patches.
For your config, do not go to System 7.5.5. If you can't get 7.0.x running, recreate your system using 7.1 plus patches.