Entrepreneurs, IT managers, IT consultants, and scientists are faced with increasing IT performance and security requirements while simultaneously needing to reduce CO2 emissions, energy consumption, and costs. Thin clients and virtualization, as well as server-based computing, offer an ecologically and economically advantageous alternative to traditional PC networks. This book provides a quick introduction to the fundamentals of these technologies and outlines the economic and, in particular, ecological benefits, based on current studies from the Fraunhofer Institute UMSICHT. Practical cases illustrate the savings and environmental advantages achieved. The content includes: energy efficiency in data centers, energy savings through virtualization, desktop virtualization, thin clients: introduction, economics and ecology, national and European environmental impacts.