{ 
 An application sends the WM_WININICHANGE message to all top-level windows 
 after making a change to the WIN.INI file. 
 The SystemParametersInfo function sends this message after an application uses the 
 function to change a setting in WIN.INI. 
}

 type
 TForm1 = class(TForm)
 private
 { Private declarations }
 procedure WMWinIniChange(var Message: TMessage); message WM_WININICHANGE;
 // or WM_SETTINGCHANGE 
 end;

 var
 Form1: TForm1;

 implementation

 {$R *.dfm}

 procedure TForm1.WMWinIniChange(var Message: TMessage);
 var
 status: Bool;
 Area: TRect;
 begin
 inherited;
 case Message.wParam of
 // Example: Detect when the screen saver is enabled/disabled 
 SPI_SETSCREENSAVEACTIVE:
 begin
 SystemParametersInfo(SPI_GETSCREENSAVEACTIVE, 0, @status, 0);
 if Status = True then
 ShowMessage('Screensaver has been enabled.')
 else
 ShowMessage('Screensaver has been disabled.');
 end;
 end;
 end;