NCR 7458 - Manual (Page 39)

Chapter 3: Hardware Service 3-15
2. Press in on the latches on the sides of the disk drive assembly. At
the same time slide the drive assembly toward the back of the
terminal using your thumbs.
Note:
Press on the top set of latches. The bottom latches are for the
Hard Drive Drawer.
20335
Latches
3. Lift the drive assembly out of the terminal and disconnect the
cables from the drive(s).