Air Cooling:

A good air cooling system for a PC requires three component categories. Heat-sinks, fans, and a case. The key here is moving as much cool air into the case as possible while getting all the hot air out. In the past, most PC cases just featured one or two exhaust fans and relied on vents to bring in cool air. Using intake fans gets in more cooler air faster though so most cases now include them. Fans come in various sizes and types. Your typical PC these days will feature either 80mm or 120mm fans. The former being the most common for off the shelf models while the latter is common in better cases designed for gaming. 120mm fans are the best to use since they can move more air than smaller 80mm ones. Since they're bigger, they also don't need to turn as fast to move more air so they're inherently quieter. The general rule is the bigger the fan, the quieter it is . Larger fans do cost more but they're better in the long run. Some case designs, however, won't fit the larger fans so you're probably going to be stuck with 80mm in those cases.

Balance is key here. You want as much cool air coming in as hot air going out. Remember that your power supply (PSU) also has a fan and that it draws air from inside the case to cool it so that counts as one of your fans. So we need to balance things so say your power supply has a 120mm fan and the case has a single 120mm exhaust fan. Therefore, an ideal setup would be to have two 120mm intake fans. Sometimes that's hard to do but try to keep it set to more heat going out if you can't match your ideal since cool air will still be passively pulled in from the outside through vents. A typical mid-tower case these days will usually have one slot for a fan at the front by the drive bay, two slots at the back of the case, your PSU fan, and a side fan. Mid-tower are the most common case type. The best setup is to set the front and side fans to intake. The front fan brings in cool air to cool the drives and addon cards while the side fan brings cool air into the CPU heat-sink. The PSU and back fan should exhaust the heat. Larger full tower cases such as CoolerMaster's excellent CM Stacker series will have more fan slots on both the front and back but the same rule of balance still applies. 

Heat-sinks. There's a large variety of them out there. Some flashy, some rather ugly. While it is tempting to get a pretty heatsink if you have a case window, remember to put form over function. A lot of these pretty heatsinks don't cool worth crap. The stock heatsinks that come with your CPU or graphics card usually do an ok job but moving to third party ones will allow your processors to run much cooler and quieter, and even leave more room for some overclocking. Most stock Intel and AMD CPU heatsinks are a chunk of aluminum with fins, a mirror finished bottom, and an 80mm or 92mm fan on the top. Third party ones will usually use copper or a mix of copper and aluminum. Copper absorbs a lot of heat quickly. Aluminum can't absorb as much heat but it likes to get rid of it fast due to it being a lighter element. A typical enthusiast heatsink will feature a copper base with thin aluminum fins. Becoming more popular is heat-pipe technology. Heat pipes are filled with an easily vaporizable liquid. They use capillary action to move the fluid. As it heats up, it vaporizes and rises up where the heat is transfered to the fins. It then moves back to a liquid and falls back down. This is more efficient that just using the older fin and block design. The block and heat pipes are usually made of copper while the fins are usually aluminum though some companies such as Zalman use copper. The liquid used in these pipes is a trade secret. I recommend using this type of cooler since they are more efficient. Buy heat sinks that accommodate a 120mm fan provided they will fit in your case. The fan on top pushes air into/through the heat sink and is more efficient than using passive fanless designs. Good ones to buy include the Thermaltake Big Typhoon, Tuniq Tower, or Thermalright Ultra 120. These aren't your only options so make sure you check out comparative reviews of coolers to see how they stack up against each other. 

To install your cooler, simply follow the instructions that came with it for your specific CPU socket type. The type of socket your processor uses will be indicated in your motherboard manual though current Intel desktop boards use LGA775 while AMD ones use Socket AM2. You'll probably have to remove the motherboard to install the cooler. First off all, you'll need to do some cleaning. Your old fan will have left thermal paste on the processor. Use a cotton ball or q-tip along with a 70% rubbing alcohol solution to remove the paste from the processor top. Most processors these days are covered with a metal plate protecting the core itself but if the core is exposed, just be a little more delicate. Even if the processor is new, you should still clean it, as well as the base of your new cooler. The next step is applying new thermal paste. Some will come with your cooler but I recommend using a silver based paste for optimal cooling. What thermal paste does is fill in any micro gaps between the processor and the heatsink base. DO NOT leave this step out or you risk frying your processor. I recommend using either Arctic Silver 5 or Antec Fromula 5 thermal paste. The former is widely considered to be the best but the latter is more widely available. Both use silver particles. Silver is one of the best elements for heat transfer but it's obviously impractical to use it for heatsinks. Silver paste is not as expensive as it sounds and a little goes a long way. Use a piece of card to spread a thin layer over the entire exposed processor core or the metal plate if it has one. Be sure not to get that stuff on any of the electrical contacts or you risk damaging your CPU. Once done, gently set the cooler onto the processor and attach it with the provided brackets. If it screws onto the motherboard, make sure to tighten the bolts firmly, but not to tight to avoid cracking the board. Next, plug the cooler's fan into the motherboard's CPU fan header, close up the case, and fire it up. You'll need to do a burn in to set the thermal paste before you try any overclocking. That simply means running the processor at full load on stock speeds for maybe 20min to half an hour. One final note on thermal paste. Make sure it's thermal paste and not thermal adhesive. The latter of which is a glue which will permanently attach the heatsink to the processor. 

You can also upgrade the heatsink on most graphics cards. The stock coolers on graphics cards tend to be either barely adequate or vary noisy so upgrading them makes sense. I personally recommend looking at Zalman's VF900 series but as with CPU coolers, you have a lot of choices. You'll need to check compatibility with the fan you want to buy, which is usually listed on their website. It's done in the same way as with the CPU. You can also upgrade the cooling for other components such as RAM and chipsets. These generally don't need additional cooling beyond stock. The CPU fan will blow cool air onto the RAM as well as the CPU heatsink. Another way to improve cooling is cable management. This basically means moving electrical and data cables inside the case out of the way to prevent them from disrupting airflow. Power supplies with modular cables are a big help here since unused power cables can be removed or added as needed. 

There you have it, you've learned about basic air cooling. Part 2 will cover basic water cooling.