Reliability measures of a computer system with independent constant failure of hardware and software components have been evaluated by using semi-Markov process and regenerative point technique. A single server is provided immediately to repair the system at hardware failure while software is up-graded whenever it fails to meet out the desired functions properly. Hardware repair and software up-gradation are perfect. The random variables are statistically independent. The failure times of hardware and software components follow negative exponential distribution whereas the distributions for their repair and up-gradation times are taken as arbitrary with different probability density functions.  The graphical behaviour of some measures of system effectiveness has been observed for arbitrary values of various parameters and costs. The profit of the present model has also been compared with the models developed under component wise redundancy.