hi, i am an anime fan and would like to save images from the anime (which is a rmvb file)!!

I tried to use the printscreen key on the keyboard to save the image, but it turned out to be totally black..
so i downloaded screenshot captor and tried to use it to capture the image, but..the saved image still turned out to be black (is i saved it into jpg file), otherwise the image was automatically saved as pcx file which my computer cant read...

Is there a way to capture and save images from the anime of rmvb file??

any help/ suggestions are much appreciated!!!

thanks!!