A flexible magnetic disk drive to be mounted between, and fastened to, a pair of opposed holder plates forming parts of the housing of a data processing instrument such as a computer or word processor. The disk drive has a base structure comprising a platform, on which there are mounted such standard components as a drive drive mechanism and a head transport mechanism, and a pair of side walls on the opposite sides of the platform. Usually in the form of an aluminum die casting, the base structure would suffer deformation if it were fastened directly to the holder plates, due to positional errors between their screw holes. The deformation of the base structure is avoided by coupling the base structure to the holder plates via a pair of connectors which are fastened to the opposite side walls of the base structure. Each connector has a pair of lugs each having a hole formed therethrough for receiving screws or like fastener elements passing through holes in the holder plates. Being less in rigidity than the base structure and the holder plates, the connector lugs are deformable to take up possible positional errors between the connector lug holes and the holder plate holes.