Lenovo IdeaCentre D400 Series Hardware Maintenance Manual page 53

7. Pull the system board tray out until you gain access to the HDD status LED
8. Disconnect the HDD status LED cable and the front USB port cable from the
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(2) Disconnect the backplane LED cable from the hard disk drive backplane
(1), then pull the backplane bracket out of the chassis (2).
and front USB port cables.
system board, then slide the tray out of the chassis.
Chapter 7. Replacing hardware