I used to be an overclocker who valued performance and robustness over sound level. Thus, I packed my case with ten fans (none larger than 80mm) and three hard drives. When my 300W power supply couldn't keep up, I stuck an additional 250W PSU in the 5.25" drivebays. I also ran Linux. Thus, the 550W Penguin, pictured on the right.
As my tastes matured, I made do with stock clock speeds, a single hard drive, and four fans - three 80mm and a lazy 120mm. I also found an attractive Penguin case (center of above photo) to keep it in. My gaming rig is still pretty noisy, but with the help of the information I've found here, I can make it quieter. It's an AthlonXP, 1.67GHz. Maxtor 100GB hard drive on paper / duct tape suspension. 120mm exhaust fan in custom-drilled hole. The case is thin-walled and very light. I think I'll pick up some deadening material from the junkyard next time I'm there and glue it to my case doors and floor. I might also buy a fanless heatsink with heatpipes for the CPU, though I have concerns about mounting such a heavy heatsink on a machine that I do transport fairly frequently.
My office app / internet box is my favorite computer. It has a Pentium processor, overclocked from 133 to 166MHz. A 6GB hard drive that whines and needs attention. Its motherboard supports SODIMM and SDRAM, PS/2 keyboard and mouse, and an ATX PSU. The PSU is the quietest ATX PSU I found in the basement, and it's a winner. It had two, now has one, quiet, variable speed 80mm fan. It has a stamped grill that I will cut out as soon as the HDD stops overpowering the sound of the PSU. Neither the Pentium processor nor the modest video card need a fan. 128MB of RAM salvaged from systems that this box outlived. This is The Little Box That Could, on the left in the pic. It runs Win2k (stripped of needless Windows services), Mozilla, Office, etc.
Edit: I should add that I have a KVM switch (highly recommended!) to switch between using the quiet one and the loud one.
Also, the original design goal of The Little Box That Could was to make a PC with low thermal dissipation, which is why I chose a Pentium rather than, say, a Celeron. I originally stripped out the fans to save heat, and I simultaneously discovered that a computer can be very quiet. I suspect this system is about 50W, while my gaming rig is about 200W. For reference, the average thermal dissipation of a human is around 100W.
