I don't recall there being password protection on System 7, 8 or 9.

That's not to say that there wasn't some Apple product that did lock down the machine, primarily for classrooms.
There was such a program but it's name escapes me right now.

How about booting from the CD/DVD, if available, and using the extensions manager to turn off all the extensions, or physically moving the extensions into an Disabled Extensions folder.
Ditto the Control Panels where you may find the Control Panel that dealt with that piece of software.
Then reboot.