Functional enhancements to the WebCom metacomputer are described which give rise to dynamic reconfigurability and extendability of the computer platform. Component modules and interactions are described, with particular attention to the communications module that enables dynamic reconfigurability. The machines of the metacomputer can be configured to act in client/server or peer to peer mode on a number of interconnection topologies such as NOWs, Clusters or Grids. This paper addresses the dynamically extendable machine structure of WebCom facilitated by this new communications structure.