get a can of compressed air and blow out the vents.
Also, after 3 years I imagine your batter doesn't hold much charge anymore, right? In those cases it starts to generate a lot of heat, needlessly so. So, if you're running on AC power, pull the battery out and see if that helps the issue a bit.
Also, make sure that your ambient room temperature isn't too high. And as a last measure you can get a laptop cooling pad. They provide some surface cooling and can help dissipate some of the heat the cooling heat sinks cannot always get to. (That is if you don't already have one)