It was always loud, but somehow it now managed to "scream" all the time, even idle.
And since she got Windows Vista (*cough*) installed on it, the HD is ALWAYS busy, even if you had not touched anything for hours, I have no idea why this crappy OS is behaving like that.
It started to really piss me off.
So I ripped out its guts ;)
I have no "before-after" pictures, as most of the time I just started to fix an annoying condition without thinking about keeping records of the process.
But I think you can imagine from my writings.
I checked the system and CPU temperature, way too high.
Almost closed case, "boxed" PC-fan, passive cooled graphics board and the only thing that ventilated all this was the tiny power supply fan.
But before modifying anything, I removed all the dust from the case, the power supply and the CPU heatsink, which wasn´t that much, compared to my own "well-ventilated" case. So that didn´t have any noticeable effect on the noise and temperatures at all.
So I decided to improve the airflow and decouple the HD.
I installed two (cheap) 120 mm fans (I had lying around) to the front of the case, one in the front bottom (hidden in the photo) and one in the middle (fixed with foam rubber and clearly visible, thought she would like it, since she just finished her Mechanical Engineering Education and likes turbines ;D ).
Removed all removable parts decreasing the airflow (intake cover etc.), and placed the 3,5" HD behind the middle fan in an 5,25" slot while acoustically decoupling it from the cheap sheet metal case (resonating body) with some PU-foam pieces.
(CPU) Temperature decreased about 20 °C (!),
high speed CPU fan not audible anymore,
instead a barely audible low-freq humming of the slow speed 120 mm case fans,
HD access is still barely audible, but not amplified by the case anymore
Overall way less than half as loud as before.
Won´t keep me from a nap on the couch now, even if it´s busy.
Mission accomplished ;)
For me 0,- €/$ since I had the parts laying around
Fans: about 10 to 20 €; even the cheap ones are still "quiet" compared to expensive but smaller diameter fans
Some PU-foam and foam rubber pieces, cents for the amount I used, about 5-10 € if you have to buy whole slabs / pieces.
Working time: About two or three hours from getting pissed to have it up and running again.
Enjoy the silence :)