After several years of this very loud PC, and a few months of using these fancy new PCs that are quiet, the whine of the old PC was getting to me. (The quiet PC in question is a Compaq with a Celeron in it. Model number unknown. Also, the Mac Mini is very quiet.)

After doing some research, it looked like the cause of the noise was a combined result of loud computer parts: the power supply fan, the fan on the CPU, the fan on the graphics card, and the hard drives. The solution offered by websites was to replace each with quieter parts.

I came up with a simpler solution: install "sound deadening" material into the case. What I used was a sheet of regular bubble wrap, and a few pieces of shipping tape to hold it in place. This was installed into the inner panel of the case.

This material, like all sound-killing material, operates by converting high frequency sounds like the whining of hard drives and fans, into a lower frequency rumble. The irregular surface of the material also reflects the sound back into the case, where it bounces around a bit, turning into "white noise". Reflected energy is also dissipated from other sides of the computer.

The computer is now somewhat quieter.

The other main strategy I can envision is to replace the three disk drives with a single drive that is quieter.