Use prime95 and intel burn test as mentioned by mouse24 also download a temperature monitoring software such as core temp, real temp or speedfan ect so you can monitor the temperature of your CPU. They will also tell you the frequency your CPU is running at and the voltage being drawn to power the CPU and the power consumption (wattage being used) of the CPU. Also CPUID is a good piece of software which will give you more detailed info on your CPU and some other hardware such as Ram ratios ect.