We are all aware that the CPU (also referred to as the “processor”) is the core engine that drives our computers. Like all machines, the CPU itself inadvertently emits heat as the feedback of its intense electrical operations. Keeping the CPU temperature within the chip limitations is ideal for having a stable system and prolonging the life of your computer.
An overheating CPU causes intermittent system hangs, random system restarts, can sometimes corrupt your data, and in extreme cases – the cpu itself may burst into flames and destroy the motherboard.
The easiest and possibly most accurate way for checking your CPU temperature is through the BIOS monitor. Most motherboards include fail-safe temperature controls that will restart or power-off the computer when the max CPU temperature is reached. While this is a good method for protecting your computer, it is still best to be proactive and check your the CPU temperature when you are using it for prolonged hours/days.
In the community of system administrators, tech support staff, and overclocking enthusiasts, some popular software for checking cpu temperature is known as follows – HWMonitor, CoreTemp, Speedfan, RealTemp, and AIDA64 (previously known as Everest).
CPUID Hardware Monitor http://www.cpuid.com/softwares/hwmon...s-history.html 
HWMonior is free software created by the CPUID Group that is also the creator of CPUZ (a hardware auditing and overclock validation tool). One of the strengths of using CPUID Hardware Monitor is that it is frequently updated for compatibility with new hardware models and brands, a zip version is available for download – you don’t need administrator access to install HWMonitor. An added feature is for checking the hard disk temperature.
Real Temp http://www.techpowerup.com/realtemp/ 
Real Temp is a temperature monitoring program designed for all Intel single Core, Dual Core, Quad Core and Core i7 processors. Each core on these processors has a digital thermal sensor (DTS) that reports temperature data relative to TJMax which is the safe maximum operating core temperature for the CPU. As your CPU heats up, your Distance to TJMax will decrease. If it reaches zero, your processor will start to thermal throttle or slow down so maximizing your distance away from TJMax will help your computer run at full speed and more reliably too. Older Pentium 4 models are not supported by RealTemp. RealTemp is also capable of checking the temperature readings on newer and supported video cards. Just like HWMonitor, RealTemp does not need administrator access to be installed on your computer.
RealTemp also has a built in in “benchmarking tool” that can simulate heavy processor usage – thus stimulating CPU activity for temperature checking. Also this benchmark may be useful for comparison and ranking of one’s system to the fastest CPU that RealTemp has on its database.
SpeedFan http://www.almico.com/speedfan.php 
SpeedFan gained popularity during the good old days of the Pentium 3, AMD Duron,, Pantium 4, and AMD Athlon processors. SpeedFan was initially sought by its users for its capability of tweaking the CPU fan speed to support overclocking. Depending on the motherboard model, SpeedFan is capable to adjusting the fan speed settings while in operation of Windows. This provides a convenient method of dynamically customizing the fan speed bios settings based on the user’s needs. In the case of reducing fan speeds this saves on power consumption and reduces cpu fan noise.
SpeedFan is also capable of checking the SMART feaure of hard drives. This provide a convenient means for checking of any hard disk errors have occurred while running Windows.
CoreTemp http://www.alcpu.com/CoreTemp/ 
CoreTemp shows the temperature of each individual core in each processor in your system! You can see in real time how the CPU temperature varies when you load your CPU. It's also completely motherboard independent.
Intel and AMD recently published detailed, public information about the "DTS" (Digital Thermal Sensor), which provides much higher accuracy and more relevant temperature reading than the standard thermal diode sensors do. CoreTemp makes use of this feature to provide accurate temperature readings.
AIDA64 – also known as Everest http://www.aida64.com/ 
AIDA64 is the latest version of the free inventory and monitoring tool that was originally called AIDA32. Seasoned computer administrators and tech support have at encountered AIDA32 or AIDA64 at least once in their hardware inventory tasks.
The latest version of AIDA64 is currently sold as a commercial software. Its hardware inventory features have been greatly improved and now caters to a larger database of computer hardware. AIDA64 is able to connect and interpret results with more hardware sensors. It also maintains its benchmark data for conducting hardware and performance tests.
Using multiple tools to find an average temperature reading
While the most convenient accurate means of checking cpu temperature is still through the reading given by the BIOS, some cases like in laptops or older desktops might not display the temperature information. It is suggested that you use at least two of the tools above to find an average or common temperature reading.
In my tests with all five tools on a desktop and laptop:
Laptop temperature reading 
It seems that RealTemp detects a much higher temperature reading compared to the other four software. Unfortunately, my Lenovo laptop’s BIOS does not provide a temperature reading so I could not verify the correct reading. I believe that the average readings done by the other four software would be most accurate.
Desktop temperature 
In my test with the desktop, it seems that three tools made a common reading. I am able to verify from the BIOS temperature monitor that the common readings made by the three software are accurate
In general, CPU cooling is best supplemented by proper case ventilation and exhaust.
In most generic computer cases, ventilation is easy to accomplish. The front intake holes can be equipped with a fan to suck cool air from the outside, pushing it to blow to the hard drives, and then to the motherboard. The back exhaust fan sucks hot air in the casing out to the rear. Some cpu cases and fans provide anti-dust filters to minimize the accumulation of dust as cool air is sucked into the casing. Of course, it is occasionally required to brush off any dust balls, and vacuum the computer case.
