The DRV_POWER message is sent to an installable driver each time the power supply to the associated device is about to be turned on or off.
dwDriverIdentifier
Specifies a unique 32-bit value that identifies the installable driver.
hDriver
Identifies an instance of the installable driver.
lParam1
Not used.
lParam2
Not used.
An installable driver returns nonzero if it processes this message. Otherwise, it returns zero.