For more, here's the original story.
Computers get hot, and they must be cooled. Your average store-bought PC uses a system of fans to pull heat off major components such as the CPU (central processing unit), graphics processor and hard drives. Then the hot air is blown out the back of the machine. That works just fine for most computers doing most jobs. But it's not always ideal, and it does nothing to impress your friends. The other option for dissipating heat is water cooling, or, really, liquid cooling, in which a combination of distilled water and propylene glycol is piped through the guts of the machine. Installing a liquid-cooling system isn't all that difficult, though it can be intimidating. Who can really benefit from this hot-rod project? Mainly, computer users who like to overclock their PCs and run them hard for gaming applications, video processing, sequencing the DNA of Amazonian tree frogs, and the like. Such people often work their processors into a heated frenzy, forcing the fans to run constantly and noisily.
Since liquid transfers heat more efficiently than air, water-cooled PCs can run significantly cooler. (In tests at Popular Mechanics, our liquid-chilled rig ran at 62.6 degrees Fahrenheit at idle - 27 degrees colder than a similar air-cooled computer.) You'll also be able to remove one or more fans, so your water-cooled system will run more quietly. Koolance, Thermaltake, Zalman and other companies sell a variety of water-cooling kits at prices ranging from $150 to $470. (You also can buy the parts piecemeal, but we suggest using a kit for your first water-cooled setup.) A water-cooling system includes a water block, hoses, pump, reservoir, and an external or internal radiator. Make sure you buy a kit that fits your PC's motherboard. It took us about an hour to hook up a Zalman Reserator 2.