Magnetic disk drive

A magnetic disk drive comprising:

• an eject plate mounted on a chassis, said eject plate being slidable in the direction of mounting and ejecting a magnetic disk by means of an external force;
• a disk holder assembled with said eject plate for holding the magnetic disk, said disk holder being slidable up and down in cooperation with the sliding movement of said eject plate;
• and a carriage mechanism having magnetic heads mounted thereon for recording and reproducing data on and out of the magnetic disk, said carriage mechanism holding the magnetic heads in a manner that the magnetic heads are movable in a predetermined radial direction relative to the magnetic disk, said magnetic disk drive further comprising:
• a locking mechanism for restricting downward sliding movement of said disk holder, said locking mechanism being provided at a position close to a front end of the magnetic disk mounted on the magnetic disk drive, wherein said locking mechanism is located at a first position to lock said disk holder, the first position being between the chassis and said disk holder when no magnetic disk is mounted on the magnetic disk drive and the locking mechanism engages with the front end of the magnetic disk when it is mounted on the disk drive and moves to a second position away from the first position between said chassis and said disk holder.