VxDs receive WM_QUERYENDSESSION and WM_ENDSESSION messages when the Windows user interface component is shut down. These notifications have the same purpose as the WM_ENDSESSION message received by Windows applications. VxDs can refuse to allow Windows to shut down during the WM_QUERYENDSESSION broadcast. For more details on the wParam values for these broadcasts, refer to the Windows software development kit (SDK).
VxDs may also receive WM_STARTSESSION, a special notification that is not sent to Windows applications or drivers.