A movable platform (50) is mounted on opposing guide rails (52, 54) within a disk drive (40). A head actuator (60) and a spindle motor (82) are mounted on the movable platform. The platform moves on the guide rails from a forward position to a rearward position upon insertion of a disk cartridge (10) into the disk drive. As the platform moves toward the rearward position, the elevation of the platform changes in order to bring the spindle motor in engagement with the hub of the disk cartridge. A latch member (138) is pivotally mounted on one of the guide rails for latching the platform in its forward position when the disk drive is not in use.