Fan Extremely Loud, NOT mechanical.

We have two hardware identical Acer L100 "bookshelf" systems with 2GB and Win 7. These tiny systems have a "drive tray" allowing for fairly easy removal of the HDD and the DVD in one unit.

I just went through nightmarish five hours with my wife's system. Situation:
The fans in computer D (her initial) run way too fast/loud, permanently.
The fans in computer E  (my initial) hum along normally.

To find out if comp D had a fan or heat related hardware problem I exchanged the drive trays; so now
E has his system (drives!)  but runs on originally D's "noisy" computer chassis,
D has her system (drives!) but runs on originally E's "quiet" computer chassis.

Guess what, E's system on formerly D's noisy chassis now runs just as quiet as before the switch;
likewise D's system now on originally E's quiet chassis makes the same terrible fan noise that D experienced before the chassis switch.

My $0.02: Something is "wrong" with D's system, OS, drivers, programs, anything software; but what?

CPU load seems to be "normal" (Task Manager), that is to say no single program or service takes 100% cpu.
No virus or other malware (Malwarebytes, a-squared, Microsoft Security Essentials).
Windows Update says all is up-to-date.
Everything non-essential is deactivated (AutoRuns).
Downloaded and installed the latest Nvidia driver; according to Nvidia "solves some reported fan problems". No luck, still noisy.

BTW, nothing, but absolutely nothing is interfering mechanically with any fan(s) in either chassis.

I don't know anymore where to look. Anybody any ideas please?
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you mentioned the DVD is part of that "drive tray".  I've seen these things make funky fan-like sounds.  Do you get a different noise with and without a DVD in there?

What if you swamp the HD only, and not the DVD?

greg wardSystems EngineerCommented:
If you can prove it , take it back to the shop and tell them its too noisy.
It could be any number of things but they should replace it under warranty.
install speedfan, and check the cpu and disk temperatures, maybe something is the cause :
you can also disable programs and services at startup with msconfig to troubleshoot
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eikeleinAuthor Commented:
Thanks to all for their attempts.

@Korbus: No, it's not the DVD. Trust me, the DVD sounds totally different and the sound should change when it's been used but the fans just keep whirring full blast with or without the DVD.

@deepdraw: Good idea - but: Do you have ANY idea about the level of competence of Acer's support? It's almost non-existent; they don't even have a support forum for their users. And the boxes are over three years old. Yes, I could just cut the loss and buy a new Asus mini system or the like but I am too darned old fashioned. That IMHO must have a software reason and I want to fix it!

@nobus: Thanks for the tip, I will try Speedfan; it will be much later today until I can get at it again and I promise I will report back.

All the others: Please keep suggestions coming, TIA.
If you swapped the fans and the formerly quiet fans are now noisy and the formerly noisy fans are now quiet, that tells me the problem is with D's
  1. Fan speed controller - no variable, just max speed, or
  2. Temp sensor - fan and speed controller are good, but temp sensor reads a false high
Either way, you lose because now you have to deal with it. Sorry. I hope they are still under warranty whether you bought them local or on-line.
eikeleinAuthor Commented:
@Lee: Thanks for your attention to the matter.

I have to disappoint you, the fan speed IS variable, just always way too fast.

The temp sensor must be working too because it needs about a minute after log on to go to full blast. And it reacts somewhat to changing work load.

@Everybody: I found the culprit, the problem is gone!In Win7 Power Settings somehow the D system got set to "High Performance", in the E system this setting was and is "Balanced".

Setting system D Power Options to Balanced IMMEDIATELY slowed the fans down and all is normal now. She is VERY happy!

Again, Thanks to everybody who tried to help. And HAPPY EASTER to all.

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tx for the feedback !
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