SpeedFan is a freeware program that monitors fan speeds, temperatures and voltages in computers with hardware monitoring 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 can even change the FSB on some motherboards (but this should be considered a bonus feature). At the lowest level, SpeedFan is an hardware monitoring software, but its main feature is that it can control the speed of the fans (depending on the capabilities of your sensor chip and your hardware) according to the temperatures inside your pc, thus reducing noise and power consumption. Several sensors, like Winbond's and ASUS AS99127F support fan speed changing, as well as others from MAXIM, MYSON, ANALOG DEVICES, NATIONAL SEMICONDUCTORS and ITE, but the motherboard manufacturer must have connected the relevant pins to some additional, yet trivial, circuitry. This means that if you have, say, a W83782D on a BP6 then you're ok, but not every motherboard with such an hardware monitoring chip will be able to change fan speeds.
SpeedFan can find almost any hardware monitoring chip connected to the SMBus (a subset of the I2C BUS), to the ISA BUS and to nVidia Video Cards. SpeedFan works fine with Win9x, WinME, WinNT, Win2k, Win2K3 and WinXP.
SpeedFan can be minimized to the tray and is compatible with Motherboard Monitor 5.

4.13 - INFO: it looks like under extreme circumstances, SpeedFan could hurt the monitor connected to an nVidia Video Card. This happened only while doing a SEND REPORT. For this reason, version 4.13 was written. Version 4.13 greatly improves nVidia Video Card support, makes sure that some, possibly offending, checks are no longer done and COMPLETELY REMOVES NVIDIA VIDEO CARD support in SEND REPORT. You can safely use the SEND REPORT facility from version 4.13 on.
This is the first serious, yet very rare to happen, issue ever reported for SpeedFan.
- SEND REPORT no longer scans nVidia Video Cards

- enabled NVIDIA video cards support after resume

- added support for WORD READs to nVidia I2C, thus detecting available LM75 sensors on that BUS

- added support for GeForce Ti 4400

- a bug tracking system is available at http://www.bugtrack.almico.com

- added detection for LPC47M172

- handled the inverse logic for PWM in LPC47M192

- less debug messages are issued when problems are detected accessing the SMBus

- made the LM75, AD7416, AD7417 temperature reading compatible with the higher resolution of the DS75

- no longer probed for DDC monitors

- removed WINBOND CLOCKS checking

- GL525SM check is now done only at $2D