I'm using Folder Guard Pro 5.4. on XP. Personally I really like it. I have a drive with all music on it (mp3). I protected it made it read only, and hidden.
The wierd and cool thing is that Windows Media Player cannot access it, nothing can it looks blank even in device manager it says the full amount of space as free, except a playlist I made of it with winamp, even when protected winamp can still play the music on it using the playlist.