FrontFace Lockdown Tool is a free tool which enables restricting or locking down any Windows user account.
The program is designed to help build a kiosk system, a public-facing PC which allows access to specific applications only. But you could also use it to create an account for your children, for instance, which limits their actions and blocks their access to many system functions.
FrontFace Lockdown Tool looks and works much like any other Windows tweaker. Settings are organised into three sections - Startup and Shutdown, Continuous Operation, Protection and Security - and each one has various lists and checkboxes covering its options..
At its simplest you might use the program to disable various Windows functions. You can prevent a user launching Task Manager, switching between user accounts, logging off or shutting down the PC, using the Windows or Ctrl+Alt+Del keypresses.
Not enough? You can also set up your PC to log into a particular user automatically, without displaying the login screen. Disable login override (holding down Shift when you boot to log in somewhere else) and it's far more difficult for a user to bypass.
Set a particular startup program and that should launch whenever your system boots. If you need more protection, change your PC's shell to that application, instead of Explorer, and the usual Explorer shortcuts will no longer be available.
Even if you stick with Explorer, there are ways to limit user actions, such as hiding any system tray icons on the Windows taskbar.
It's also possible to shut down, hibernate or reboot the PC at a set time each day. If you're building a kiosk PC this should help you keep any maintenance to a minimum.