Asus AP1720-E2 - Manual (Page 62)

Chapter 2: Hardware setup 2-42
5. Press the fan case hooks outwards
until the fan detaches from the
case.
6. Slightly press the center of the
fan vent to flush the fan out from
the case. Set the HDD fan aside.
4. Locate four hooks inside the
HDD fan case.
To re-install the HDD fan:
1. Insert a new HDD fan to the fan
case until it clicks in place..