Economic theory and business strategists have pointed at the phenomenon of positive externalities and the related enabling and constraining aspects of an installed base. For instance, in the development of a standards strategy for technology products these externalities are of profound importance [11]. Likewise, deployment of large-scale IS creates interdependencies horizontally throughout the organization, and are constrained by a continuously evolving and socio-technical installed base of information, systems, artifacts, practices, and organizational structures. This paper draws from a case study of a global company and illuminates the role of an installed base in relation to the organizing visions in the deployment of a large-scale IS. The case illustrates that deployment of a large-scale IS in a global company is likely to be more similar to the development of infrastructures than traditional IS development and ITstrategy planning.