If you are unable to watch the downloaded videos on this website you are missing some video codecs. The easiest way to solve this problem is to download a codec pack or a media player which supports most of the video codecs.

Codec Packs
The two most popular codec packs are XP Codec Pack and K-Lite Codec Pack, however there are some more free codec packs, all can be found and downloaded for free on this website.

Media Player
Another easier way to view the videos is by downloading a video player which supports most videos.

VLC Player - Download
Media Player Classic - Download