My daughters Pc is an acer E360 which has a custom motherboard made by foxconn FC51GM. I isolated the high speed fan noise down to the power supply.
Disconnected all case fans including the cpu cooling fan to do this. The Athlon XP 3500+ could almost run without the cpu fan just the heatsink connected. Only ran about 10 degrees higher with the brief disconection of the cpu fan.
The problem is that no matter what power supply I put in there the power supply fan runs at full speed and sounds like a jet engine. They run all run at around 1500 rpms. Even an Antec truepower which is supposed to run low and quiet unless the system is running at or near max.
This is a low power system CPU 45 Watts. ATI Radeon HD 4650 75 watts at full load which it never even comes close to. 2 gigs of ddr400. It runs windows 7 with ease. The noise is the same running windows XP or 7 not that this should make a difference.
This is a non gaming pc. Just surfs the web and does her home work with open office.
I tried speedfan to control the fanspeed but not sure how to use it or if it will work to control the power supply fanspeed. will try to find a speedfan tutorial.
Very very annoying to listen to. Doesn't bother her much but I know it should not be running at full speed constantly.
I changed to an msi board with 3 fan speed settings in the bios, one for the cpu heatsink, and two for the case fans. I set it at fifty percent, and the case fan runs below one thousand. A few antec power supplies have a three pin lead to the motherboard that may work with smartfan. But most boards I've used don't have a speed setting for the case fans, only the cpu. Next time you change boards, download the motherboard bios manual first and check the settings. I use an ocz ps with 140mm fan, and they are very quiet. You might find a scythe fan that will fit in your ps, but any ps is high voltage, so you have to be carefull changing out the fan. Some are soldered on, and some have a two pin connector to the ps board.
Can you monitor the PSU voltages? Some motherboards have this ability (don't know about Foxconn, never dealt with them). I'm wondering if your voltages are stable. It might be possible something on the board is bad and causing unnecessary power-draw.
It might also be as simple as the other case fans not doing their duty. If the inside of the case gets too warm, the PSU has to run its fans at higher speed to get better cooling. Is the air coming out the back of the PSU very warm? How about the air coming out the back of the PC itself (presumably driven by a case fan), is that very warm? You might just need better airflow. I'm honestly amazed at the pathetic amount of airflow some of these OEMs design into their cases, especially when they offer 3-year warranties that have to cover over-heated component replacement. You can try running the thing with the side off. See if the PSU will slow-down the fans with better access to the cooler outside air. That is, assuming you don't have the PC right next to a heater vent. If its drawing hot-air from outside the case that's even worse.