Abstract: A structure for protecting a removable HD comprising a casing for receiving the HD, a terminal adapter for connecting to terminals of the HD at one end, the terminal adapter including terminals at the other end, a seat for releasably securing to the casing, and a circuit board mounted in the seat, the circuit board including terminals adapted to releasably connect to the terminals of the terminal adapter. The casing comprises a positioning member (e.g., latch) at one end and two lengthwise rails formed along its both sides respectively. The seat comprises a mated positioning member (e.g., transverse positioning bar at one end) and two elongate grooves formed along its both sides respectively. The rails are adapted to slide along the grooves, and the mated positioning member is adapted to lockingly engage the positioning member when the casing is inserted into the seat.