If you really don't want to get a new graphics card, get an aftermarket VGA cooler (like this one:
http://www.newegg.com/Product/Produc...82E16835118117) but really it's better just to get a better card. Best AGP card I can find is a Radeon 4650:
http://www.newegg.com/Product/Produc...82E16814125281 There's also a Radeon 4670 but it's by PowerCooler and I'm not familiar with the brand. Make sure your power supply is adequate.