History of cooling -

In the early days of computer cooling, when vacuum tubes were still new, cooling wasn't that important, as electronic parts could used at high temperatures. However, as more vacuum tubes were used, th vacuum tubes themselves needed cooling, and lots of it. Air conditioning and liquid cooling were used to try to cool the tubes down.

However, when transistors were invented in the 60s, the need for newer cooling was apparent, as the transistors generated less heat but in a smaller area, and also were more temperature sensitive.

Computers sometimes got there own floors, so that they could make maximum use of air conditioning system, and other components, like disks, were put in different rooms. Hard drives, though more effecient per size than tape drives, were much more temperature sensitive.

Integrated circuits, or chips, generated even more heat per area. More compact fans and heat sinks were used. However, this wasn't always enough, and liquid cooling was born. Components were assembled around a large heat sink, around which water could flow, easily riding the system of heat.

Common Problems -

Dust, caught in the computer for years, can build up and insulate the parts, holding heat in.

The air current the fans are making could actually hurt, as it can create whirlpools of hot air.

It is important to clean out your computer and adjust the fans properly, the computer could overheat, or just have too much heat can cause more wear and tear on all the parts.

If you are trying to overclock the system, cooling is more important, as the computer is easier to overheat, and any warranty is null and void. Make sure you have good cooling before you overclock, or you will regret it.

Make sure your fans are in the right place, and that you have an adequate amount. You want to have an intake fan for every outtake fan, though if you have an odd number of fans it is better to have an extra outtake fan.

Buying it

The best place is New Egg

http://www.newegg.com/Store/Category.aspx?Category=11&name=Fans-Heatsinks

The more expensive fans are simply covered in LEDs, or are silent fans, meaning they will spin silently, or are easier to install, or all three. They don't offer better performance.

Another option is the "silent Computer"

All the fans are silent. Though they are quiet, they aren't as efficient. Overclocking is not so possible with these

The point of a cooling system is to cool your computer. An air cooling system uses heat sinks and fans to dispearse heat, drawing it away from parts that could be damaged by heat. Even if the parts will still work with heat, heat will cause them to wear and tear more quickly. A more effecient cooling system will save you money in the long run.

Also, with a well cooled system you can overclock your processor. This can save you a boatload of money, as you don't have to spend much money on a new processor, as your old one will be able to keep up with the times. This will shorten thre life of your old processor, but it is worth it.

The Main ways of cooling a system is heat sinks, which is a large metal block with many folds/prongs in it, which greatly increases the surface area. This allows the heat to be transferred faster from the hot area to the air. Heat sinks are made from a highly conductive metal, such as copper of aluminum. However, aluminum is better in that it can be formed easily by extrusion (is able to be pushed or pulled through a mold to make a specific shape). New research is being done in synthetic-diamond and phase change material heat sinks.

The next step and another important component in the cooling system - the fan. The processor/card fan take the hot air heated by the heat sink and blow it away, allowing the heat sink to allow heat to continue down its gradient via the 2nd law of thermodynamics and keeping the heat generator cool. Then the case fans circulate the air, taking in cool air and blow out hot, creating a current that helps disperse heat.

To be effective, the heat transfer must reach an equilibrium - the same amount of heat being generated is being dispersed. If more heat is being dispersed, that is a waste of energy, but if it is the other way around, the part in question could melt.

There are many things that could hurt the ability of the computer to cool itself. dust, caught in the computer for years, can build up and insulate the parts, holding heat in. also, the air current the fans are making could actually hurt, as it can create whirlpools of hot air. It is important to clean out your computer and adjust the fans properly, the computer could overheat, or just have too much heat can cause more wear and tear on all the parts.

if the heat in a critical part has approached a dangerous level, thermal sensors will pick up the value of heat and shut down the computer, or throttle back the electrical usage of the part.

Controlling

The cooling system is controlled by three methods - user controlled, sensor controlled, and static controlled. Static controlled parts are like most stadard fans - they run at the same speed always. Sensor controlled fans run on a speed determined by tempurature sensors conected to the motherboard. Usually they are found on the CPU and other chips. Lastly are the user-controlled fans. They can be adjusted by a fan controll dial on the case, or maybe in the BIOS. Not all computers have a fan controll, but the ones that do are good.