The purpose of the present paper is to carry out Cost-Analysis of a computer system of two identical units. Each unit comprises hardware and software components which may fail completely directly from normalmode. There is a single server who inspects the unit at its hardware failure to see the feasibility of repair. If repair of the hardware components in the unit is not feasible, the components are replaced by similar new one with some replacement time. However, only replacement of the software components in the unit by new one ismade at their failure with some replacement time. The failure time of the unit due to hardware and software failure follows negative exponential, while distributions of inspection, repair and replacement time of the components are considered as arbitrary with different probability density functions. There is an independenthardware and software failure in the unit. The expressions for various measures of system effectiveness are derived using semi-Markov process and regenerative point technique. The graphical study of the results obtained for a particular case has been made.