Sometimes you'll have an out-of-warranty video card that's now basically a paperweight.
If you were going to throw it out anyway, you can try your luck at temporarily repairing the card by re-flowing the solder—heating and reseating the metal balls under the die. All you need is an oven and some good luck.
Obviously, as with any guide that involves an oven, you might burn your hands, burn your house down, inhale toxic fumes, and other hazards, so please don't do anything that you're not comfortable doing.
However, if you're confident and the potential of a repaired card is worth it to you, continue through the guide.
(Please note that the guide has been edited by a few people over the years - some parts are not my original writing!)
-Gaspard (and editors)
Graphics cards' circuit boards can have bad solder joints under the GPU die, which can sometimes be temporarily fixed by heating the board in an oven.