2000Rpm is pretty much the standard idle speed. I think I may have seen them go as slow as 1800 before but at 2000RPM it should be almost silent. When the CPU/GPU is on max load it should spin upwards of 5000RPM. Now 75C or 167F is pretty hot, these chips should be able to withstand at least 95C or 203F. The part the is concerning is while 75C is definitely ok for the CPU the fans should be spinning faster than 2000RPM at that temp. You they should be somewhere between 3 to 4k, and making a little noise. If they are not spinning up that high their maybe either a driver or controller issue. I would boot into Mac and run something CPU intensive and see if they fans don't speed up more around that temp. If they seem to work better under the Mac OS you may have an issue with a driver in windows. I would also look into the program TimeAgentGamer listed above.