@Wilse
But you're gonna find it hard to get a hard drive that's ultra-quiet, and even harder to get a silent PSU. They do exist though.
I don't know about that. It's easy to get quiet PSUs around here, just about every shop has them. They cost 50% - 100% more than your average noisy PSU though. I use a QTechnology Papst series PSU in my PC and it's almost noiseless (if you put your ear next to it you can hear low whirr from the fan).
Western Digital make hard drives that are pretty low-noise, and Hitachi (formerly IBM) drives are pretty silent too.
You can also put sound dampening stuff into your case. I bought some cheap engine compartment sound insulation at a car parts shop and stuck it all over the inside of my PC case and now it's very quiet, almost unhearable (my VCR makes more noise than my PC now). Just make sure you have good ventilation in your box since the sound insulation is also heat insulation (wouldn't recommend using it without a case fan).