We have cable modem internet service for our desktop computer. With password another device in the home can receive the wi-fi signal. There is no router and the wi-fi signal comes from the modem which is plugged in to the wall 24/7. We turn the desktop pc off at night.
We need to limit the wi-fi to 11pm cutoff to 7am start. I had a simple timer plugged into the wall and the modem cable was plugged into that and the timer let the modem go off at 11pm and on at 7am. The timer failed to prevent the guest from changing the setup.
There is another closed question about a lockbox, how to secure the cable modem or timer so no one can unplug the setup and then plug the modem into the wall socket for 24 hour access. So no need to repeat the content in that other question.
Windows 7 desktop and parental controls would only limit access to the desktop pc.