Lenovo C2 Series Hardware Maintenance Manual page 42

Step 5. Remove the hard disk drive cover. Refer to "Replacing the hard disk drive".
Step 6. Remove the speaker cover. Refer to "Removing the speaker cover".
Step 7. Remove the 4 screws that secure the computer cover to the chassis.
Step 8. Remove the computer cover as shown.
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Lenovo C2/C3 SeriesHardware Maintenance Manual