2–10 Maintenance and Service Guide
External component identification
Bottom components
Item Component Description
(1) SIM slot (select models only) Contains a wireless subscriber identity module (SIM). The SIM slot is located 
inside the battery bay.
(2) Hard drive bay Holds the hard drive and a Bluetooth device.
(3) Memory module compartment Contains the memory module slots and a wireless LAN module slot.
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To prevent an unresponsive system and the display of a warning 
message, replace the WLAN module with only a module authorized for 
use in the computer by the governmental agency that regulates 
wireless devices in your country or region. If you replace the module 
and then receive a warning message, remove the module to restore 
computer functionality, and then contact technical support through Help 
and Support.
(4) Vents (3) Enable airflow to cool internal components.
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The computer fan starts up automatically to cool internal components 
and prevent overheating. It is normal for the internal fan to cycle on and 
off during routine operation.
(5) Battery release latch Releases the battery from the battery bay.
(6) Battery bay Holds the battery.