I wouldn't recommend it, but then again video card manufacturers have a tendency to put higher energy requirements on video cards to avoid being blamed by people who have a crappy psu's. I highly doubt that a 250 w psu could handle the card, and the potential of frying your components is just not worth the risk. Instead I would recommend buying a high quality psu and replacing the one you have. It's a fairly simple process and you should go to newegg.com to find one that fits your price range and requirements.