Abstract: An improved magnetic disk drive system including a rotatable disk, a shiftable carriage having a pair of read-write heads mounted by resilient arms thereon for coupled relationship with the disk, and a stepper motor for advancing and retracting the carriage and thereby the heads with respect to the disk. A locking mechanism is shiftably carried by a fixed base forming a part of the system, the mechanism including a locking member moveable between the resilient arms, whereby the arms are spread apart and the heads are moved away from the disk to prevent contact of the heads with the adjacent surfaces of the disk. The movement of the blocking member is a function of the movement of the carriage into its fully retracted position. Moreover, the member effectively locks the carriage against movement when the carriage is in the fully retracted position thereof.