|Most video players have the option to do a screen capture and save it to a bmp or jpg picture file by pressing a key on the keyboard. |
Irfanview is a good picture/video viewer. While viewing the video in Irfanview, press the C key and it will save the screen capture to the irvanview folder. VLC is another good player that can capture screen shots. I'm not sure of the hotkey but it will tell you in the help section. or you can set it to whatever you want in the options section.
Irfanview - www.irfanview.com
VLC - http://www.videolan.org/vlc/