The DRV_ENABLE message is sent to an installable driver when it is loaded or reloaded or whenever Windows is reinstalled after switching to an MS-DOS application.
dwDriverIdentifier
Not used.
hDriver
Identifies an instance of the installable driver.
lParam1
Not used.
lParam2
Not used.
An installable driver returns zero if it processes this message.
When the DriverProc function receives this message, it should initialize all of the driver-specific structures with default values.