Type .mpg at the end of your search name.

Sounds like you're lacking codecs to play other types of videos. Get them from here: http://lists.gpick.com/pages/CoDecs.htm OR http://www.free-codecs.com/ OR http://www.land.ee/d_nimo_codec.html

You might be wise to also get a backup player like VLC which has built-in codecs & plays almost everything: http://www.videolan.org/vlc/ (choose nearest mirror site)