Lenovo ThinkCentre M91p 4524 Hardware Maintenance Manual page 146

7. Press the optical drive lock
Figure 74. Removing the old optical drive
8. Install the optical drive retainer on the side of the new optical drive.
Figure 75. Installing the optical drive retainer
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ThinkCentre Hardware Maintenance Manual
1 and slide the optical drive out of the rear of the drive bay assembly.