Like other members said, it is possible but it requires some careful planning. Don`t forget that fans are not the only component spinning and thus making noise. You will also need to address the disk drive(s) which are louder than a couple of low speed fans in my experience.
Having said that, it is certainly an interesting thing to try and there are many useful links in this thread.
If I were to build a fanless pc today it would go like this:
M/B: I would certainly go for a motherboard with intergrated graphics. One reason is power consumption, the other, is that a dedicated vga would restrict the natural convection airflow a little.
For an intel cpu I would reccomend theese boards:
Dvi, but average reliability record
Good all rounder but no dvi
Hdmi, good features but expensive
HDD: While the GP is a good all rounder you might consider a notebook drive such as these:
Even lower power consumption than the GP, designed for laptops ie to work in a low airflow environment.
Even those laptop drives can be audible. I ended up sandwiching my hdd between foam and another larger drive and got good results by doing it.
PSU: A pico psu would be ideal. It uses no fan and takes up very little space inside the case since it uses an external power adapter. The most power efficient solution for a minimal system.
A lesser, 80 watt combo is available in Greece, not sure if it can take a core2 at full load.
You will need a few adapters to connect your components to it:
If it must be an atx psu, I would reccommend this rebranded fortron:
http://www.pc-store.gr/product_details. ... tem_id=495
I think that the pico is worth the trouble though, it will be more difficult to manage the airflow in the case when you add the bulk of an atx psu.
CASE: In a passive setup you will probably want to use natural convection airflow to it`s full extent. That means you need a case with large vents at the top and bottom.
I see two possibilities: you can either pick a decent case you like and cut the vents yourself, or you can choose a case that already has those. The only one I could find was the coolermaster 690, pics shown here:
It`s available in checkmate though you might also find it in eshop (currently out of stock).
If you choose another case and wish to modify it, a lian li might be a good choice as aluminium is easier to cut than steel. You will also need some grills unless you are really confident in your cutting skills
Any vents that do not contribute to your cooling setup should be blocked, especially at the front. You might also want to use sound deadening materials to further reduce hdd noise.
HEATSINKS: A skythe ninja and thermalright hr05 could handle the cpu and chipset. The mosfets that regulate the power to the cpu will probably need some cooling as well.
I`m afraid there is nothing in the market designed for mini atx motherboards. A solution is to cut/adapt an old heatsink you already have. If it`s not possible, at least try to fit some vga ram heatsinks.
Shop around in eshop for those.