So when the Radeon HD 4870 gets busy with a very graphics-intensive application and gets hot, the fan spins up. Not to a troublesome level, mind you, but enough to hear the whine in my super-quiet PC at home. In fact, some users are more concerned about the GPU temperature and have set the fan to manually spin at around 35–40%, claiming you "can't hear it." If I do that, I definitely hear it. It all depends on how much noise the rest of your machine makes.

So I stopped by my local PC white-box shop, Central Computers and picked up a Zalman VF900-Cu VGA cooler for $40 (you may find it, or similar products, online for a bit less). It's made to fit a variety of cards, including Radeon HD 3000 series; almost all the coolers that fit 3000 series cards fit the new 4000 series. After 15 minutes with a small screwdriver, it was installed and ready to roll, still taking up two slots as the card did before.