SimpleMonitorOff is a Windows application which powers off your screen (or screens) when you lock your computer.
When you lock your computer (eg. with Win+L) then ordinarily your screen(s) may not power off. SimpleMonitorOff detects that you have locked your computer, and broadcasts a message to Windows requesting that the screen(s) be powered down. Shortly afterwards your screen(s) will power down (ie. go into standby mode).
When you move your mouse or hit a key, they will wake again to let you unlock the computer.
If you (or your cat) did that by accident, then after a little while your screen(s) will power down again.
Note: Unlike many similar applications, SimpleMonitorOff does not require any additional hotkeys, mouse clicks, or shortcuts – it responds to events sent by Windows itself, so will respond to you locking your computer however you choose to do it, rather than expecting a specific hotkey combination or shortcut.
SimpleMonitorOff v1.x is compatible with Windows Vista onwards.
It has been explicitly tested with Windows 7 and Windows 10, but should work with all compatible versions of Windows.
You will require local administrator privileges to install it but thereafter it will work fine with Standard (a.k.a. Limited) User accounts.