Distributed computing, the exploitation of idle cycles on pervasive desktop PC systems, offers the opportunity to increase the available computing power by orders of magnitude (10-1,000 times). However, for desktop PC distributed computing to be widely accepted within enterprises, the systems much achieve high levels of robustness, security, scalability, unobtrusiveness and manageability. We describe the Entropia distributed computing system as a case study, detailing its internal architecture and philosophy in attacking these key problems. In particular, key aspects of the Entropia system include the use of (1) scalable Web/database technology for system management, (2) network tunneling and application name-spaces for logical connectivity, (3) binary sand-boxing technology for security and unobtrusiveness, and (4) an open integration model to allow applications from many sources to be incorporated. These technologies are combined to produce a robust, flexible, high-performance system which is now in use in numerous enterprises, supporting a wide range of applications.