You lack the video decoder required to play the video.

A common video decoder many people do not have and need to play some video files is DivX. You can go to http://www.divx.com/ to get the codec. I think it may be in a bundle. You should stay away from the free pro bundle, as it contains spyware.

Another one is XviD, which is an open-source decoder that handles its own algorithm as well as DivX 5.x's and a few others'. You can find it at: http://www.xvid.org/. It is not as efficient at using other algorithms as its own.

If the video decoder you need is not DivX, then you may need to find out what it is. Use the tool here to find out what decoder you need to play the file: http://www.headbands.com/gspot/download.html

If you cannot find the decoder after you find out what it is, and it is not DivX or XviD, post the name of the decoder required to play the file in this topic. We can help you find it.

Additional note: A "codec" is the combination of an encoder and a decoder. That might be what the sites offer and that is what you need to get.

Good luck.