Zalman Northbridge Heatsink
My Zalman NB47J heatsink arrived today. This evening, I spent an hour or so removing the old fan and replacing it with the new heatsink. It was fairly easy to do, but I did have to completely remove my motherboard from the case to install it. The chipset fan is held in place by two spring-loaded pins that clip down into holes in the motherboard. I tried to push the pins back through the motherboard, but it was too difficult, and I didn't want to risk damaging the PCB. So, I snipped them with a pair of wire snippers. I then applied some new thermal grease (supplied) and attached the Zalman heatsink, using the same holes in the motherboard to attach it. It's a tight fit next to my graphics card, but there are a couple millimeters of clearance.
The best news is that the chipset actually runs cooler with the passive heatsink than it did with the active cooling fan. So, that's good news all around. I get a quieter case as well as a slightly cooler chipset.