This issue has been addressed by many, but I would like to add my two cents. On a HP Z800 or similar box. You might encounter the case fans going full speed non-stop. There are two things to check
Inside the BIOS is a tab called temperature it has a bar display and is adjustable make sure you have it turned all the way down (maybe the opposite way) in ether case it should do something. If it does nothing...
Next thing might be the temperature sensing transistor located on the top right of the box looking from the front. It's buried inside and is a real hassle to get to. These transistors really don't go bad, they are being used as a temperature sensing device with the BASE connected to the COLLECTOR making a temperature sensitive super diode. It may have gone out of speck
the number on mine was 2N3404 (NPN) a cheap simple part 10 cents. I didn't have one so I used a 2N4126 (PNP) wired the B to the C and soldered it in backwards because it's the opposite polarity transistor.
Since I did both, the transistor first I really don't know which was the real cause. The point is that this is a hardware issue not an operating system issue. The right side of the case comes off
with the removal of two screws from the bottom. The transistor is inside of shrink wrap stuck into a hole. With a razor knife you expose it and replace it. Hopefully one of these two fixes works for you.