Complex sentence: What the user would do is remove the drive from its case and then loosen the screws holding the stepper motor that moved the head, then with the calibration disk in the drive gently turn the stepper motor back and forth until the program showed a good alignment.
Split into simpler sentences: What the user would do is remove the drive from its case and then loosen the screws holding the stepper motor that moved the head. Then with the calibration disk in the drive gently turn the stepper motor back and forth until the program showed a good alignment.