A computer set for coupling to a disk drive and a battery unit, includes a disk-drive connecting port, a power diverter circuit and a power source. The connecting port includes a set of disk terminals, a set of battery terminals, and a set of power terminals. The diverter circuit is coupled electrically to the connecting port. The power source is electrically coupled to the diverter circuit such that when the computer set is coupled to the disk drive, the sets of disk and power terminals are electrically coupled to the disk drive and the power source supplies a first electrical power for the disk drive via the diverter circuit. When the computer set is coupled to the battery unit, the sets of battery and power terminals are coupled electrically to the battery unit so as to permit the battery unit to supply a second electrical power for the computer set via the diverter circuit.