CPU Fan run in full speed

[BBeta]

HP Compaq dc7800 small form factor
I have a problem with the CPU Fan it running in full speed all the time ...
I read that I Should update my bios I do that but nothing happened
I cleaned the fan and nothing happened
I changed the fan with a new one and nothing happened
I try with SpeedFan but it can't detect the fan ...
so please where is the problem in this case !!!!

 

[cklaubur]

Does Speedfan show your CPU temperatures? If so, what are they?

Casey

 

[BBeta]

Yes it shows CPU temperatures, but in : configuration -> fans I can't see any fan !!!

 

[cklaubur]

Programs like Speedfan seem to have trouble with detecting fans, and sometimes even temperatures, on preassembled computers, like your HP/Compaq or my Dell laptop.

However, my concern is whether your computer is just dealing with a software issue and the fan running at full speed is a symptom, or whether it thinks it is (or may even actually be) overheating, which will also run the fan at full speed.

Let's just play it safe and make sure first.

Casey

 

[BBeta]

For the Second concern there isn't any overheatingة CPU Usage doesn't use more than 30% for the most time.
For the first concern maybe true, but how I can know who's causing the fan trouble ?!

is reinstalling the OS can help ?
Note: when I boot from ‘buntu live CD the problem still Exists !!!