First I tried to just replace the fan in the back of the case - which had not much effect.
So then about a month ago I decided to take the plunge and bought the following components - all German-made with quiet in mind from the outfit called quietpc.co.uk:
New case - 60
Power supply - 60
CPU Cooler -
The plan was to take all the innards from my old pc and move to the new, save for the new cooler (enormous metal contraption - 16cm tall, weighs about a kilogram) and the quiet power supply.
Found a guy on Craigslist to come over and do the operation. He came, spent about 3 hours in my living room but in the end the computer wouldn’t turn on - the old motherboard refused to work outside the original HP case.
I went online and bought a new motherboard - Asus P9X79. The first guy didn’t want to come back for reasonable money, so I found another guy to do it.
He shows up - and turns out that the motherboard I got is a wrong size for the case (case is micro-ATX while the new mb is full-ATX).
I order a new case from Germany and return the other case.
Guy comes over - installs the MB, everything seems to work.
After he leaves I realize that Windows only recognizes 1 DIMM out of 3. I play around with various DIMMS / slots combinations and recognize that all components are fine but MB only recognizes one DIMM at a time.
Look up the issue online - turns out the pins on the motherboard CPU socket could be bent - which causes the issue. Extremely weird - as I ordered the mb new and I never heard of cpu bending the socket pins during insertion. I also expected the computer to not boot at all in this case.
I call the guy over to see if the pins can be unbent or maybe we try to reseat the CPU. Nothing works - but the pins are indeed bent, but really too small (maybe 1-2mm tall) to do anything with.
I order another motherboard. Guy comes over and installs it. Everything works. PC is so quiet I can’t hear it.
Whole process took about a month.
Cost of components - about 300 GBP (might be more if I choose to go further a fan-less video card - as that’s the only source of pc noise now)
Labor - 115 GBP
Overall the story was plagued by two unforeseen issues
1. Original HP motherboard refusing to work in a generic case
2. New Asus motherboard having bent socket pins
and one fuck-up on my part
1. Ordering a regular ATX motherboard for a micro-ATX casе
Overall I'm happy with the result. Would certainly prefer to make do with a smaller time wastage - but after all it's not that hard to watch other people work :)