SpeedFan is a freeware program that monitors voltages, fan speeds and temperatures in computers with hardware monitor chips. SpeedFan can even access S.M.A.R.T. info for those hard disks that support this feature and show hard disk temperatures too, if supported. SpeedFan supports SCSI drives too. SpeedFan can even change the FSB on some hardware (but this should be considered a bonus feature). At the lowest level, SpeedFan is an hardware monitor software that can access temperature sensors, but its main feature is that it can change fan speeds (depending on the capabilities of your sensor chip and your hardware) according to the temperatures inside your pc, thus reducing noise and power consumption. SpeedFan can help you to build your own silent pc. SpeedFan is an extremely powerful tool. It can help you a lot to find the reasons for an unpredictable reboot or for a failing hard disk. It can tell you whether you are likely to experience temperature related issues and can help you to greatly reduce the noise at work or while using your HTPC. But this great power requires access to a lot of resources on your motherboard and it might be that your hardware does not like such kind of access. SpeedFan is used worldwide since 2000 and there are so many happy users out there, but you should always remember that no program can be perfect and that I can't be held responsible if SpeedFan causes any damage to your system.