xps 420 fans running high all the time.

Dell xps 420 cpu fan, case fan and gpu fan run @100% high from when the desktop is powered on until it is shut off. The cpu temps monitoring software shows cpu temps well below 40 C. Even with no load stress the fans are constantly running on high (it sounds like a hairdryer on high). All components are dust free, and the desktop is clean.

Any advice greatly appreciated.

Dell xps 420 (build)