The hard drives are definitely one of the loudest components in the computer, so taking care of those was an absolute necessity. The advantage of water cooling them is that then they don't need air flow and you can encase them in sound proofing material. Here I'm putting on the funky thermal paste that Koolance uses for their HD-60. It goes into the space between the hard drive spindle/circuit board and the water block and hardens into a foam-like substance. It was pretty messy when mixing it, though.