Power cards can generate quite a bit of heat, and laptops have limited ventilation, as it is. Also, if the inside is dusty, that'll just make it worse. If you can, get some canned air from an office supply store and blow it out near the vent. You could also use a compressor if you've got one, but they're not considered "static-safe". Also, if you keep it on all the time, I'd suggest that you either turn it off or hibernate it at least at night before bed. You can also buy one of those laptop cooler fan things to rest it on while you use it. If not, you can do what I did when mine was overheating. Set it on top of a phone book or stack of magazines while letting the side that has the vent be exposed in order to maximize the air flow to keep it cool. Laps, carpets, blankets, and all the things laptop users rest our compies on can generate heat.