Remove the Lower Fan from the computer tower.
Lay the computer on its side; you will see a blue knob.
Turn this knob 90 deg clockwise.
Slide the panel case forward about 1/2 inch while knob is turned.
Lift panel case off computer.
Remove the large blue cover from the computer. There are no screws or tabs holding it in place.
Remove the power supply that connects the lower fan to the motherboard, distinguished by it's black, red, green and yellow wires.
Remove the rubber grommets from the base of the fan. A spudger may be useful.
Press on the blue release tab and remove the fan.