2. SpeedFan: SpeedFan is a program that monitors voltages, fan speeds and temperatures in computers with hardware monitor chips. SpeedFan can even access S.M.A.R.T. info and show hard disk temperatures. SpeedFan supports SCSI disks too. SpeedFan can even change the FSB on some hardware (but this should be considered a bonus feature). SpeedFan can access digital temperature sensors and can change fan speeds accordingly, thus reducing noise. SpeedFan can find almost any hardware monitor chip connected to the 2-wire SMBus (System Management Bus (trademark belonging to SMIF, Inc.), a subset of the I2C protocol) and works fine with Windows 9x, ME, NT, 2000, 2003, XP, Vista and Windows 7. It works with Windows 64 bit too.
3. Real Temp: Real Temp is a temperature monitoring program designed for all Intel single Core, Dual Core and Quad Core 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 throttle or slow down so maximizing your distance away from TjMax will help your computer run at full speed and more reliably too.
4. HWMonitor: HWMonitor is a hardware monitoring program that reads PC systems main health sensors : voltages, temperatures, fans speed. In addition, it can read modern CPUs on-die core thermal sensors, as well has hard drives temperature via S.M.A.R.T, and video card GPU temperature.