The Preop medical expert system (Langton et. al, 1990) was originally developed using the expert system tool, Nexpert Object, on a VAX computer. Nexpert Object creates an expert system specification which is executed by an interpreter within Nexpert Object. The original implementation, however, has several limitations, including: 1. lack of physical portability 2. requires Nexpert Object to run 3. crude user interface. In order to overcome the first limitation, Preop is implemented on a PC DOS portable computer. This project is addresses the other two limitations. Creating a compiled version of Preop eliminates the need for the Nexpert Object interpreter, and implementing it as a Microsoft Windows application provides a better user interface. / Thesis / Master of Science (MSc)