What card do you have? Are you overclocking the card? Do you know what kind of temps the card is reaching? Do you have the latest driver for the card installed?
i have a GeForce GT 610, not sure if i'm overclocking the card i haven't made any adjustments myself, the latest driver is installed, and it wasn't heating up i have it well ventilated and it is in a really fresh room in open space, it usually takes 2 hours or more for it to do this to me.