Ohm's Law is the Law of Physics that defines the basic relationship between resistance, current, and voltage in any given electrical circuit. It also defines how each of those affect power consumed. Ohm's Law is commonly expressed in the simple mathematical equation:

I = E ÷ R

...where I = Current, E = Electromotive force (voltage), and R = Resistance. By extension, "power" (P) in watts is commonly expressed by the equations:

P = I x E or,
P = I² x R

Ohm's Law is showing that increasing voltage in a circuit, as done with overclocking, causes the current in the circuit to increase. When current goes up power consumption goes up, and so does heat - the bane of all electronics. The problem is compounded because when heat goes up, resistance goes down, which increases current, which increases power, which increases heat and so on and so on. When that cycle gets out of control, it is called "thermal runaway" and results in tripped safety devices, if lucky, smoke, fire and destruction, and in extremes cases, loss of life, if not. Students of electronics are well aware of that, and regulation and protective circuits are included in designs. However, the engineer's design rarely survives those who control the purse strings and the quality and capability is often less determined by the design specifications, but rather budget, assembly and manufacturing quality, component quality and tolerances, and the scruples of the factory manager.

Obviously, low quality and low budget devices are less immune to abuse - and overclocking is abuse, make no mistake. Overclocking places a greater demand on everything on that bus, the motherboard's regulator circuits, power supply, case cooling, CPU and CPU cooling, chipset and chipset cooling, and more. Even if all goes well, some components are running warmer than normal which affects device aging. It is not just running warmer or hot for long periods, but the temperature swing from cold to hot is wider, resulting in more extreme contraction/expansion cycles as the "matter" cools and heats. This causes "fatigue" or microfractures in the materials, adversely affecting aging too.

From a technician's standpoint, one who has to clean up the mess afterwards, I am always amazed when a fried overclocked machine comes in and the user is in a panic because his entire life is on that machine.

I find it interesting, disturbing, and a deceptive marketing ploy by motherboard makers who are building in overclocking capabilities, and bundling overclocking utilities with their new motherboards. From an engineering standpoint, you don't build in "overclocking capabilities" - you design to meet the requirements, with standard textbook overheads necessary for "expected" variables (operating environments, supply voltages, component tolerances, etc.). It is the "marketers" and "advertising companies" that are trying to reach that "risk-taking" enthusiast in all of us by "dummying down" published specifications so folks can feel good about bumping it up a bit.

The facts are damages that can be attributed to overclocking or excessive heat from overclocking are not covered under warranties by the motherboard makers, RAM makers, Intel or AMD. If you overclock and fry the CPU, your loss. If the CPU overheats and takes out the socket destroying the motherboard, your loss. If the power supply goes too and takes out everything with it, your loss.

I am not totally against overclocking, it can be a fun challenge, especially when experimenting with alternative cooling too. And when done in a lab under controlled and monitored conditions, this "stress testing" may provide insight longterm reliability. But it should be understood that overclocking is a hobby that requires a lot of homework, and a greater commitment to hardware health monitoring and preventative maintenance. Losses should be expected. If the computer is needed for work, school or personal business, it should not be overclocked! At the very least, ensure a robust backup plan is in place, and used often.

And never overclock an unstable computer.

If you want more power and better performance, I recommend buying it.

As a little side note - some PCs used in home theater systems where any fan noise is bad, underclocking is used to keep systems cool, and therefore quiet. ...but it works.