as above - if all you're doing is watching movies, then there is no need for a separate video card UNLESS your motherboard doesn't give you an HDMI connector directly.
if you have a fairly old machine that doesn't have HDMI output, or you play games, or you need to use graphics card video decoding - then you might need to get a video (graphics) card.
95% of the time, though, you don't need it for movies.