This message is sent when the Windows initialization file, WIN.INI, changes. Any application that makes a change to WIN.INI should send this message to all top-level windows.
wParam
This parameter is not used.
lParam
Points to a string that specifies the name of the section that has changed (the string does not include the square brackets).
The WM_WININICHANGE message may be used as either a wide-character message (where text arguments must use Unicode) or an ANSI message (where text arguments must use characters from the Windows 3.x character set installed).
To send the WM_WININICHANGE message to all top-level windows, an application can use the SendMessage function with the hWnd parameter set to 0xFFFFFFFF.
Although it is incorrect to do so, some applications send this message with lParam set to NULL. If an application receives this message with a NULL lParam, it should check all sections in WIN.INI that affect the application.
SendMessage