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

procedure TForm1.Button1Click(Sender: TObject);
 var
   wnd: HWND;
   i: Integer;
   s: string;
 begin
   wnd := FindWindow('notepad', nil);
   if wnd <> 0 then
   begin
     wnd := FindWindowEx(wnd, 0, 'Edit', nil);

     // Write Text in Notepad. 
    // Text ins Notepad schreiben. 
    s := 'Hello';
     for i := 1 to Length(s) do
       SendMessage(wnd, WM_CHAR, Word(s[i]), 0);
     // Simulate Return Key. 
    PostMessage(wnd, WM_KEYDOWN, VK_RETURN, 0);
     // Simulate Space. 
    PostMessage(wnd, WM_KEYDOWN, VK_SPACE, 0);
   end;
 end;


 // To send keys to Wordpad: 
  {...}
   wnd := FindWindow('WordPadClass', nil);

   if wnd <> 0 then
   begin
     wnd := FindWindowEx(wnd, 0, 'RICHEDIT', nil);
   {...}