//На русский
procedure TForm1.Button1Click(Sender: TObject);
var
  Layout: array[0.. KL_NAMELENGTH] of char;
begin
  LoadKeyboardLayout( StrCopy(Layout,'00000419'),KLF_ACTIVATE);
end;

//На английский
procedure TForm1.Button2Click(Sender: TObject);
var
  Layout: array[0.. KL_NAMELENGTH] of char;
begin
  LoadKeyboardLayout(StrCopy(Layout,'00000409'),KLF_ACTIVATE);
end;