Thanks for this great HOWTO! I now have full control over the CPU fan and noise level has been reduced considerably. However the two chassis fans still make quite a lot of noise. They seem to be running at a constant full speed. I have one fan sucking in and one blowing out. They are not equipped with any RPM sensors and are parallel coupled from the same source. It doesn't seem to be a way to tweak them in the BIOS setup either.

Is there a way to reduce the voltage going out to these fans and by that way reduce their speed? I know this is possible by installing hardware and tune the voltage manually but I wondered if there is a way to do this with fancontrol or any other software.

My sensors readout:
Adapter: PCI adapter
Core0 Temp:  +34.0C                                    
Core1 Temp:  +27.0C                                    

Adapter: ISA adapter
VCore 1:     +1.14 V  (min =  +0.00 V, max =  +4.08 V)   
VCore 2:     +4.08 V  (min =  +0.00 V, max =  +4.08 V)   ALARM
+3.3V:       +3.30 V  (min =  +0.00 V, max =  +4.08 V)   
+5V:         +6.85 V  (min =  +0.00 V, max =  +6.85 V)   ALARM
+12V:       +12.54 V  (min =  +0.00 V, max = +16.32 V)   
-12V:       -15.46 V  (min = -27.36 V, max =  +3.93 V)   
-5V:         +4.03 V  (min = -13.64 V, max =  +4.03 V)   ALARM
Stdby:       +6.85 V  (min =  +0.00 V, max =  +6.85 V)   ALARM
VBat:        +3.15 V
fan1:        872 RPM  (min =    0 RPM)
fan2:          0 RPM  (min =    0 RPM)
M/B Temp:    +32.0C  (low  =  -1.0C, high = +127.0C)  sensor = transistor
CPU Temp:    +28.0C  (low  =  -1.0C, high = +127.0C)  sensor = transistor
Temp3:      +128.0C  (low  =  -1.0C, high = +127.0C)  sensor = disabled
cpu0_vid:   +1.550 V