Not quite as advertised, this download is merely 16 WAV files designed to be loaded into your system sounds. Vista to XP Sound Theme isn't packed as a theme you can load on your own. Executing the file places the files in your Windows Media folder. The program then automatically changes your system sounds to the packed 16 WAV files. It doesn't go the extra step, though, and you'll need to save them as a theme yourself.
Vista to XP Sound Theme also fails to back up your previous sounds. You need to make sure you do that yourself before installing these. Finally, the included sounds are not actually the default Vista sounds. With this freeware download, you may get a nice collection of Windows sounds, but don't expect what its title promises.