There are so many topics to cover regarding system thermals that it will be helpful to break this up into two discussions.  Part I, which you are now reading is an introduction of some basic concepts and some recommendations that will give you an immediate and dramatic improvement in performance.

Why does a computer produce heat?

Modern computers are miniature versions of the enormous computers that took up an entire room 20 years ago.  They are both made up of electrical and mechanical switches, albeit extremely small now.  As the speeds have increased, those switches are toggling between 0 and 1 (off and on) extremely quickly which generates heat.

Why should I manage heat?

Dissipating heat properly will increase the performance and life of your computer system components.  This is similar to your car engine where heat buildup can cause you to loose horsepower and ultimately destroy your engine.  That is why your car uses oil to reduce friction, and a radiator with coolant to reduce heat buildup in the engine block.

What features does my computer use to manage heat?

Heat naturally moves from warm areas to cooler areas at relative speeds to the conductivity of the material.  (Since both heat and electricity are forms of energy, it is sometimes helpful to think about materials that conduct electricity well.  These materials will usually conduct heat well also.)

• Heat sinks - heat conductive metals designed in a series of fins to provide maximum surface area to transfer heat from whatever it is attached to, into the surrounding air.
• Fans - Provide air circulation to move the warm air away from the heat sink
  Upgrades

Upgrades

1. The first upgrade to make is to make sure you have high quality, quiet fans in your computer case.  If you are starting from scratch, it's worthwhile to pick a quality case with several fans in a variety of locations in the case.
2. The second thing to consider is to upgrade your heat sink and fan that are attached to your CPU chip.  Higher quality heat sinks have lots of very thin fins and are often made of more conductive materials such as copper.  Upgrade heat sinks will also have a better quality fan.
3. CPU coolers with heat pipes are a great upgrade as they employ technology similar to your car radiator.  They use liquid filled heat pipes, usually made of copper, that are attached to your CPU and move the heat through a series of fins directly against the fan.  You get improved heat dissipation and improved airflow.
4. There are several other types of coolers that are less mainstream which are discussed in Part II.
5. Thermal Grease – when you attach a heat sink or cooler to your CPU, you have metal on metal with tiny little air bubbles between the two surfaces.  Air is a poor conductor so Thermal grease is used to fill the space between the surfaces and to dramatically improve the heat sink or coolers ability to keep the CPU cool.

If you are a PC gamer, you have probably spent just as much, maybe more on your video card as you spent on your CPU chip.  Heat will kill the performance and life of your video card just as it will with your CPU.

1. Video card coolers use elaborate wide heat sinks attached over the video card. 
2. They can also use a thin fan to move air across the heat sink fins.
3. Better video card coolers also use heat pipes.
4. Gaming cases will also have a fan mount near to where the video card is mounted in the case.  There is no reason why you cannot carefully cut additional fan vents in your case if you find that you need more air circulation.

If you are an experienced builder, or this is your first system, you will be pleased with the performance increases you experience when you use this knowledge to cool your computer.  If you have already taken advantage of these tips, you may find Part II informative.  In Part II, we will cover silent cooling and advanced cooling methods.