Case is ignored in the device name, but there must not be any leading or trailing blanks. Note that the device type is the pszDeviceType element of the open data structure, but it does not have a corresponding flag because it is required and does not have a command-string parameter. Also, if automatic type selection is desired (through the extensions or EA section or INI), the file name (including the file extension) must be passed in the pszElementName field, the pszDeviceType field must be left NULL, and the MCI_OPEN_ELEMENT flag must be set.

If a parent window handle is specified, but the window handle is invalid, the overlay device opens successfully, but uses HWND_DESKTOP as its parent.