Old computer: Dimension XPS Gen 3, stock except for the 4GB RAM and the NVidia 9800GT. Was a victim of the notorious jet-engine-fan-noise-and-won't-even-go-to-BIOS problem until Dell gave us a new PSU.
Don't buy the above because it WAS the best computer (in 2006) and it has a loud fan.
New computer: Current model Mac Mini with 2.5GHz i5