it will paste the entire desktop into paint and sometimes just a black screen where the media is, alot of times prt screen won't capture video snapshot depending on what is displaying it and the format. But they are correct in that you may on a lap top push a button labeled FN to set functions to work, like the built in keypad option on your keyboard. I got that turned on by mistake once and thought my keyboard was fucked until I realized what had happened.
VLC media player is free and has a snapshot option.