The operating system sends the DBT_DEVICEREMOVEPENDING device message when the device is about to be removed. This message is the last chance for applications and drivers to prepare for the removal of the device.
To send the DBT_DEVICEREMOVEPENDING device message, the operating system sends the WM_DEVICECHANGE message with wParam set to DBT_DEVICEREMOVEPENDING and lParam set to the address of a DEV_BROADCAST_HDR structure identifying the device to remove.
dwData = (DWORD) lParam;
Return TRUE.
This message cannot be denied.