WD TV™ Mini media player is an easy, affordable way to watch digital media on your big screen TV. Simply plug in WD’s My Passport portable hard drive, or similar USB drive, and play movies, music, and photos in a wide variety of file formats, including Real Media (RMVB) format. There’s no limit to the size of your media collection; just add more drives for more movies. Supports DVD-quality video playback. Also works with most popular USB drives, digital cameras, and camcorders.
I actually own this and have used it for 12 months or so - it plays all the videos I have thrown at it.