A better cooler isn't going to fix that. The point of a cooler is to radiate heat away from the component, in this case, the graphics card. A cooler cannot actually stop the heat from occuring, as that would defy the laws of the universe as we know them. Instead, it simply puts it where its not harming anything, aka into your case, or ideally, into the room the computer is in. So in otherwords, a better cooler would keep more heat away from your graphics card, but there would still be an equal amount of heat coming from your computer. Besides, gpu coolers are big, and if your computer only has a pci slot, then I'm guessing that it wouldn't be able to fit one.