Zephyr is an expanding software company that developed a knowledge management system designed to support the work of employees and provide management overview. Despite strong management support the system was not much used and instead employees themselves developed a competing and much used parasitic system. First, we argue that the failure of the management's system is caused by the concept of knowledge upon which the system was built. Hence, design of computer systems is as much a question of critical conceptual understanding of its application domain as a question of doing ethnography and system development. Second, we argue that the process of design extends far into the process of use and that much can be learned by looking at the process of appropriation of a new system. The problems of conceptualisation and appropriation point towards the need to critically examine the mangle of practice in which artefacts, actors and organizations intertwine