Lenovo ThinkCentre M55e - Manual (Page 28)

2. Remove the front bezel by releasing the three tabs and pivoting the bezel
forward to remove completely.
3. Slide the drive bay assembly forward until the drive bay assembly is aligned
with the two slots on the sides of the chassis and remove the drive cables from
the system board. Then pull upward on the handle 1 on the drive bay
assembly to remove it completely from the computer.
4. Remove any parts that might prevent access to the memory connectors.
20 Hardware Replacement Guide