A computer system with hardware redundancy has been analyzed stochastically by conducting preventive maintenance of hardware after a pre-specific operation time ‘t’ (called maximum operation time). A single server is provided immediately to the system for carrying out the repair activities such as hardware repair, software up-gradation and preventive maintenance. All repair activities carried out by the server are perfect. The failure time of the hardware and software components follow negative exponential distribution whereas, the distributions for hardware repair, software up-gradation and preventive maintenance times are taken as arbitrary with different probability density functions. The expressions for some important reliability characteristics of the system model have been derived in steady state by using semi-Markov process and regenerative point technique. Graphs are drawn to depict the behaviour of mean time to system failure (MTSF), availability and profit function under different sets of assumptions on the parameters. The profit of the present model has also been compared with the model Malik and Munday [2014].