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?