WinLockr is a free software to lock windows.
Lock your computer so that other users can’t enter without your password.
USB-Unlock: Unlock Windows by simply inserting your USB flash drive to your computer.
Mouse/Keyboard blocking: WinLockr will block the mouse and keyboard except the keys that you need to enter your password.
Shutdown Prevention: Every shutdown/restart/log off actions will also be blocked by WinLockr.
FullScreenLock: Hides the Windows interface so other Users can’t see what you were doing on your computer.