A possible way to gain an understanding of how a knowledge system works is to imagine an expert-client situation. We are all experts in our fields, but in daily life, we need assistance from an expert in an area that we do not know. This paper describes a knowledge-based system on Computer hardware diagnosis. Intermediate computer users can diagnose their hardware using the knowledge base in the system when facing some hardware problems with desktop computers. The main purpose of this paper is to include a real-time example of how a knowledge system can be built.