interesting. i'm also concerned with noise in my impending upgrade. my 4 yr old gateway can be heard 40 feet away in the other end of the apartment. it's awful! saddest thing is, i've just gotten used to it over time, so where it used to grate on me, now i barely notice it. i'm afraid it's causing subtle high frequency hearing loss over time with all the hours i put in front of it. i've pretty much decided i'm either going with a dimension 8300, or a precision 450/650 workstation. i notice dell mentions silent "quietcase" technology on the workstations, but i'm seeing conflicting information on whether the workstations or dimensions are noisier. can others confirm? am i in for a dissapointing experience if i go with the workstation?
I bought a Dell Dimension P4 from last summer. Its CPU cooling is different. Instead of having a small, high RPM fan mounted on the heatsink, it has a larger, slower RPM fan attached to the back of the box and and an "elbow" corner enclosure directing air to the heatsink. I think this is the reason it's surprisingly quiet. This is such a simple yet intelligent application of CPU cooling (plus the fact that the entire back of the box is screen-type mesh for venting), I will look for it when I purchase my next. Could be only Dell has it though.
I just recently bought an 8300 from Dell and am simply amazed at how quiet it runs . . . It contains a basic 7200rpm HD from Western Digital.
For your older machine, have you tried replacing the chassis and cooling fans with quieter models...these can be bought for just a few dollars (CompUSA, CDW, etc) and can make a big difference! Also, I have a few DELL Dimension workstations, and they are very quiet...