It should fit your motherboard fine, but make sure you have a GOOD 500 watt PSU, if its rated at peak or provides less than 400 watts on its 12 volt rails it does not count as good.
A seasonic 500W isnt very expensive and is very good quality. If you dont have a strong enough PSU you have a couple options, the card wont get enough power and wont perform well, the PSU will auto shutdown whenever you play a game, or you will have a firecracker go off in your case and need to buy a new PSU and possibly other components too. http://www.corsair.com/cinema/movie.aspx?id=622747