Enterprise Centralized Desktop and Virtual Server 2005 R2

Licensing

Windows Vista Enterprise Centralized Desktop can be licensed for both PCs and thin clients:

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  PC license. In addition to Software Assurance, an annual Windows Vista Enterprise Centralized Desktop subscription purchase is required for the PC. With this annual subscription, companies can install an unlimited number of copies of the guest operating system on any number of physical servers, as long as the VMs are accessed only by licensed client devices. Users can access up to four running VM instances on up to four servers per subscription license.
  
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  Thin client license. For thin clients, a single annual subscription purchase is required. With this subscription, companies can install unlimited copies of Windows Vista Enterprise or earlier operating systems, such as Windows XP Professional or Microsoft Windows 2000 Professional, on any number of physical servers, as long as the VMs are accessed only by licensed client devices. Users can access up to four running VM instances on up to four servers per subscription license. In addition, the annual subscription has Software Assurance built-in and provides for earlier versions, and well as upgrades that are made available within the license time frame.
  

SoftGrid Application Virtualization is licensed through the Microsoft Desktop Optimization Pack, which also requires that the client devices be covered by Software Assurance.