Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

// The Documented way 

{ 
  An application can check if a window is responding to messages by 
  sending the WM_NULL message with the SendMessageTimeout function. 

  Um zu uberprufen, ob ein anderes Fenster (Anwendung) noch reagiert, 
  kann man ihr mit der SendMessageTimeout() API eine WM_NULL Nachricht schicken. 
}

 function AppIsResponding(ClassName: string): Boolean;
 const
   { Specifies the duration, in milliseconds, of the time-out period }
   TIMEOUT = 50;
 var
   Res: DWORD;
   h: HWND;
 begin
   h := FindWindow(PChar(ClassName), nil);
   if h <> 0 then
     Result := SendMessageTimeOut(H,
       WM_NULL,
       0,
       0,
       SMTO_NORMAL or SMTO_ABORTIFHUNG,
       TIMEOUT,
       Res) <> 0
   else
     ShowMessage(Format('%s not found!', [ClassName]));
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   if AppIsResponding('OpusApp') then
     { OpusApp is the Class Name of WINWORD }
     ShowMessage('App. responding');
 end;