I have an Intel QX6850 (retail box) and DP45SG (retail box) setup and ATI 4870 1GB graphics. I am using default values for performance (i.e. non-overclocked) with fans controlled by the board (1x 120mm rear, 1x 120mm front, and the stock QX6850 CPU fan). With Windows Vista Ultimate 32bit installed, for some reason on legacy applications (i.e. Diablo, Diablo 2, Starcraft, old Emulators, etc) the CPU fan ramps up to what sounds like FULL SPEED ahead. If I minimize the legacy game window or exit it, the fan immediatly returns to slow fan speeds. As you may or may not be aware, these legacy games have little options to push the limits of the CPU or graphics hardware. Both the ATI software and Intel's Desktop Control Center reports temperatures within normal ranges. While the CPU fan is ramping up, the case fans continue to run at their normal temperature speeds (not increasing or decreasing much at all so that it's noticable). If I load up games such as COD4 or World of Warcraft, there are no fan noise issues except during brief and occasional higher loads. Dust is not an issue in this case. Ventilation and airflow is excellent - the air coming out of the fan ports does not feel hot at all. Anyone have any ideas on what the cause could be? I don't have this problem (with the same games) on my i7-920 with the DX58SO mobo.