1900 to 2000RPMs is an average for the stock fan that comes with the Intel i7-2600k and the temperature threshold should be 72.6°C.
In regards your 2 main concerns.
1) The processor’ fan is always pushing air to the processor in order to keep the processor under the temperature threshold of 72.6°C. So that is normal.
2) The RPM reading seems to be fine, what is not normal is the high reading temperatures. Most of the motherboard manufacturer (specially on extreme series) has an option on the BIOS to set the processor’s fan in to “aggressive mode” which let the processor’ fan to run at the fastest speed all the time. You may want to check this option with the board manufacturer.
Hi, thanks for your answer, nowing that it's not a faulty fan, I checked the bios and set fan speed to maximum. It's a little bit better (i.e. at rest at 50°c) but when I do intensive computing (h264 video conversion), it still gets very hot and I will probably get a better fan in order to keep it cooler.
Thanks again for your help,