uh...... i think the classic way is when u r playing a video..click the 'print screen' button on your keyboard then go to 'paint' or photoshop' or any kind of drawing program like that then click 'ctrl v' then the pix shows up then just click ' save as'
when i wanna make some caps out of a vid, i do this way all the time cuz its easy
or try to search for a program called CaptureX at
http://www.download.com
but this software has a lot of spyware in it.....maybe u might not want to install it....
there might be some other ways which u can make caps but i dont noe anything else beside these 2 ways so ......