Re: -- Computer restarts automatically? --
Umer,
Keep in mind that the onboard measurement facilities are often inaccurate and may report temperatures that are too low. This is especially the case with motherboards that use a thermal sensor below the CPU to "guess" the CPU temperature. The temperature values displayed by the BIOS have usually a correction value added, to compensate for this problem - but in some cases this correction value may be too low, or the sensor might not be in good contact with the CPU
This means: If the maximum allowed temperature for your CPU is 95°C, and your motherboard reports a CPU temperature of 90°C, then you are not on the safe side
However, this doesn't mean that you should start to panic when your CPU reaches 60 degrees celsius, for example. Most people tend to underestimate normal CPU operating temperatures - maybe due to overclockers bragging with their super-low CPU temperatures
Also, overclocked CPUs may run unstable even if their temperature is way below the maximal specified temperature
If your cooler is insufficient and the temperature exceeds the maximum operating temperature, then this does not mean that the CPU is automatically damaged. With AMD CPUs, you will usually encounter crashes if the CPU is overheated; but these go away as soon as the CPU is cooler again. In the long term, running the CPU at a temperature that is too high may reduce the CPU life, since an overheated CPU is more prone to electromigration - even if it runs stable. With P4 CPUs, the CPU will turn its speed down automatically when it overheats. No damage to the CPU is possible, but the system will get slower while it's hot (which, in some cases, users might not even notice)
If you attempt to operate a CPU without heatsink at all, recent AMD CPUs will usually be permanently damaged within seconds, unless special protection is available on the motherboard (Like IBM S5X series). P4 CPUs will run excessively slow without cooler
Umer, you may or may not have encountered cooling-related websites, which states lower temperatures typically correspond to better products. Well to bust the bubble of surprise, the opposite is true: The higher temperatures a CPU can withstand, the less cooling is required. CPUs with low electrical power, but high temperature rating can be used with more quiet and more compact coolers. An example for such a CPU is the Pentium-M, which dissipates less than 25 watts, but may reach temperatures of up to 100°C. The worst-case example is the Pentium 4 Extreme Edition 3.46GHz, which dissipates over 110 watts, but may only reach a maximum temperature of 66°C. Obviously, you need a large and possibly loud cooler then...
Rest is later on CPU theory, hope you got the idea...
Todd