Ah man you beat me to the FRAPS post. Yeah I use fraps. Mostly for gaming because you can have it running in the background.
but fraps is really laggin badly sometimes for me .... i dont really like it ..... expecially in gaame when u wanna record something lag like the pc gonna die xD
Google VLC Media Player. Download and install this. It has just about every video and sound codec known to man so It will work with anything. Install it. Not open is and goto File>Quick Open, and open w/e file you want. Under the video tab there is a snapshot option. Its saves the snapshot to "my pictures"