I actually just had to mod out my brothers for that very reason. What brand is it? Sometimes they come with a cooler on it, but it isn't efficient enough.
Or, better yet...try this. Take off the side of your case. Now get a big *** floor fan and crank it up to high. Place the fan so that it blows into your case. Now try to run a 3d application and see if it lasts any longer.