Fault diagnosis is one of the most important application domains of expert systems. Most of the diagnostic expert systems have concentrated on building systems for simulations diagnosis and have overlooked the user's need for the interpretation of the reasoning lying behind the decision. In the architecture of the system in concern, the knowledge-base is separated from the logical inference engine accordingly a shell is created and can be used as an addon to any existing knowledge-base without altering its logical inference engine. The proposed expert system features have also the facility of updating the knowledge-base in use by removing or adding rules, generating appropriate tests to support the diagnostic system, and providing extensive explanations. In this paper an intelligent knowledge-based system is developed dedicated for troubleshooting in the IBM PC, in which the proposed expert system shell implemented is through the PROLOG programming language