Well, naturally you should clean the PC including the card. That would be the first thing to do. Get a can of compressed air and CAREFULLY blow the dust out. If the card has been in constant use for over a year, it might be time to change the thermal paste between the card's heat sync and the GPU. When it gets dried out, it looses its ability to transfer heat. Then make sure there is good airflow through the case. Don't leave the case sit on a fluffy carpet that can close off the air vents, and make sure the PC is open to room air.