Hi alan, We've achieved very low noise on a 64-bit machine with the following: Panaflo 92mm Hydrowave-bearing High-CFM fan on the CPU (FBA09A12H-1BX from CaseCooler.com) 4 CoolerMaster rifle-sleeve bearing LED fans on the back (TLF-R82 from Xoxide.com) 1 120-mm Coolermaster TLF-S12 for the blowhole. (from jab-tech.com) Acoustifan silicone fan gaskets, and heavy-duty �Quiet Feet� from QuietPC. (http://www.quietpcusa.com). Also used a Vantec Power Supply Vibration Dampner Kit (CaseCooler.com) All airflow is passive on the front, active on the rear. Not silent, but very-very quiet, and very cool as well. hth, Maluvia