I just thought I would post a comment and commiserate about the iMac fan noise. Mine has been whisper quiet for about 11 months, but in the last few weeks the fan seems to be louder than normal. It is not "loud" by PC standards but there is a hum which also has a high pitch depending on how close I sit to the machine. istat says my fans speeds are 600, 1000, and 1300 rpm and termperatures range from 35 to 65°C, pretty normal I think. I've done a SMU and NVRAM / PRAM reset with no effect. I've also modified the power management plist to stop the hard drive after 1 minute to see it it was the drive motor rather than a fan, but its not. Also, and much less frequently, there is the odd "chirping" sound coming from the fans. At first I thought it was the birds outside, but then I woke up and realized its winter and the windows are all shut! 🙂 Anywho, I'm not sure if I should bother with getting it serviced since the whole computer has to be completely dissassembled to get at the fans. However, when the room is quiet, its very audible...and annoying.