MSDN писал(а):
SC_MONITORPOWER
Sets the state of the display. This command supports devices that have power-saving features, such as a battery-powered personal computer.
The lParam parameter can have the following values:
-1 - the display is powering on
1 - the display is going to low power
2 - the display is being shut off
А вообще сначала надо было проверять а потом утверждать что это не то.