[madiazg]

Muchas gracias a los dos. Un pequeño ejemplo:

procedure TForm1.Button1Click(Sender: TObject);
begin
  with TRegistry.Create do
    try
      RootKey := HKEY_CURRENT_USER;
      if OpenKey('\Control Panel\Desktop\', False) then begin
        Label1.Caption := ReadString('WallpaperStyle');
        Label2.Caption := ReadString('TileWallpaper');
        CloseKey;
      end;
    finally
      Free;
    end;
end;