![background image](http://html.mh-extra.com/html/hp/probook-645-g4/probook-645-g4_maintenance-and-service-manual_2173983008.webp)
Bottom cover ..................................................................................................................................... 33
Battery ............................................................................................................................................... 34
Memory .............................................................................................................................................. 35
Hard drive .......................................................................................................................................... 37
Solid-state drive ................................................................................................................................ 39
WWAN module ................................................................................................................................... 40
WLAN module .................................................................................................................................... 42
Keyboard ........................................................................................................................................... 43
Internal frame ................................................................................................................................... 47
Fan ..................................................................................................................................................... 50
Heat sink assembly ........................................................................................................................... 51
TouchPad button board ..................................................................................................................... 54
TouchPad ........................................................................................................................................... 56
Near Field Communication (NFC) module ......................................................................................... 57
Smart card reader .............................................................................................................................. 59
USB board .......................................................................................................................................... 61
Power button board .......................................................................................................................... 63
System board .................................................................................................................................... 65
RTC battery ........................................................................................................................................ 69
Speaker .............................................................................................................................................. 70
Fingerprint reader assembly ............................................................................................................. 71
Display assembly ............................................................................................................................... 73
Using a USB keyboard or USB mouse to start Computer Setup (BIOS) .......................... 81
Navigating and selecting in Computer Setup ................................................................................... 81
Restoring factory settings in Computer Setup ................................................................................. 82
Updating the BIOS ............................................................................................................................. 82
Determining the BIOS version ......................................................................................... 82
Downloading a BIOS update ........................................................................................... 83
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