Beware, the Shuttle AK31/AK31a boards do not have much room around the CPU for large fans. You may have to make a simple modification to it to get larger fans to fit. Examples of fans that do not fit (by default) are larger Taisol HSFs, ThermalTake Volcano 5/6/6+. To get these and other large HSFs to fit, you must make a modification to the Northbridge cooler. The cooler is a small heatsink with a fan on it. The heatsink has two tabs in opposite corners, like almost all motherboards, with plastic pins that apparently hold the unit to the motherboard. Unfortunately the pin will come in contact with the bottom of larger heatsinks, causing them to not be properly seated on the CPU. The fix is to remove the offending pin. No worry, on ALL of the Shuttle AK31/AK31a boards I've seen (probably over 30 of them) the heatsink had something else gluing them to the Northbridge and didn't rely on the plastic pins to hold it on. You can also make this a reversible procedure by pinching the pin from the underside of the motherboard so that you remove it intact.