The fan is held in place by friction. The little metal clips have triangular ends that hold the fan in place. I usually remove the whole assembly with the metal tin metal housing to remove the fan just avoid the occasional slip and destroy the PCB accident. The metal housing assembly (the fan and a silver "tray") is held in place by 2 clips with friction. You insert a long thin metal screwdriver into the second or third row on the top of the heatsink and pull up (either from the left or right side of the heatsink), then repeat with the bottom part of the heatsink and the the whole fan assembly contraption should come off. Then you can just insert a small flat blade screwdriver into each corner of the fan and pry up the fan from the metal bracket.