Virtual Distro Dispatcher (VDD) is a distributed system whose aim is to project virtual, fully operational and multiple operating system instances on terminals in a network. Client terminals can be obsolete PCs or energy saving thin clients managed by a powerful, multiprocessor (and possibly clustered) central system. VDD gives users the possibility to use their own favorite operating systems, at the same time, on each single thin client (Desktop-as-a-Service). System performance has been put to the test based on a method for coupling system monitoring with desktop benchmarking. Furthermore, privacy issues have been taken into account, considering the relevance they have in Cloud Computing. The right to act without observation becomes even more important in Desktop-as-a-Service (DaaS) environments. The book describes the design, implementation and experimental evaluation of a progressive privacy solution for a DaaS system. A client-side proxy has been introduced in VDD such that non-intelligible VDD contents and non-traceable VDD actions are guaranteed by means of homomorphic encryption, oblivious transfer and query obfuscation schemes enabled by the proxy.