The videos are using the DivX codec, so unless you have it installed (and probably one of the latest versions), you will only hear the audio portion of the clips.
DivX is available for Windows (98/ME/2K/XP) and Mac ("Mac" and "Mac OS X") and
NOTE that this form has a section for your e-mail address, but you do not have to give it to them (unless you like spam
).
http://www.divx.com/divx/download/