Abstract: A compact system unit for personal computers wherein system hardware components are closely integrated and packed resulting in an effective utilization of space. Such compact integration of hardware is facilitated by the arrangement of system hardware components co-planar with each other. The compact system unit incorporates a hard disk and a floppy disk. The floppy disk controller card is co-planar with and plugs directly on to the mother board. A bus expansion card is vertically mounted to the mother board whereby up to two additional optional expansion cards may be incorporated in a parallel formation within the compact system unit. The daughter board is directly mounted to the mother board in inverted orientation.