Each Windows Server 2008 R2 edition provides key functionality to support any sized business and IT challenge. Learn more about each edition in depth by clicking the logo or links provided.

	Windows Server 2008 R2 Foundation  is a cost-effective, entry-level technology foundation targeted at small business owners and IT generalists supporting small businesses. Foundation is an inexpensive, easy-to-deploy, proven, and reliable technology that provides organizations with the foundation to run the most prevalent business applications as well as share information and resources.
	Windows Server 2008 R2 Standard is the most robust Windows Server operating system to date. With built-in, enhanced Web and virtualization capabilities, it is designed to increase the reliability and flexibility of your server infrastructure while helping save time and reduce costs. Powerful tools give you greater control over your servers, and streamline configuration and management tasks. Plus, enhanced security features work to harden the operating system to help protect your data and network and provide a solid, highly dependable foundation for your business.
	Windows Server 2008 R2 Enterprise is an advanced server platform that provides more cost-effective and reliable support for mission-critical workloads. It offers innovative features for virtualization, power savings, and manageability and helps make it easier for mobile workers to access company resources.
	Windows Server 2008 R2 Datacenter delivers an enterprise-class platform for deploying business-critical applications and large-scale virtualization on small and large servers. Improve availability, enhance power management, and integrate solutions for mobile and branch workers. Reduce infrastructure costs by consolidating applications with unlimited virtualization licensing rights. Scale from two to 64 processors. Windows Server R2 2008 Datacenter provides a foundation on which to build enterprise-class virtualization and scale-up solutions.
	Windows Web Server 2008 R2 is a powerful Web application and services platform. Featuring Internet Information Services (IIS) 7.5 and designed exclusively as an Internet-facing server, it offers improved administration and diagnostic tools to help reduce infrastructure costs when used with a variety of popular development platforms. With included Web Server and DNS Server roles, as well as improved reliability and scalability, this platform allows you to manage the most demanding environments — from a dedicated Web server to an entire Web server farm.
	Windows HPC Server 2008*, the next generation of high-performance computing (HPC), provides enterprise-class tools for a highly productive HPC environment. Windows HPC Server 2008 can efficiently scale to thousands of processing cores and includes management consoles that help you to proactively monitor and maintain system health and stability. Job scheduling interoperability and flexibility enables integration between Windows and Linux based HPC platforms, and supports batch and service oriented application (SOA) workloads. *Windows HPC Server 2008 R2 will be available in early 2010
	Windows Server 2008 R2 for Itanium-Based Systems delivers an enterprise-class platform for deploying business-critical applications. Scale database, line-of-business, and custom applications to meet growing business needs.

For further information on the different editions please click here
 

Windows Server Licensing Overview

Microsoft offers flexible, cost-effective options for licensing the Windows Server 2008 and Windows Server 2008 R2 family of products. Prior to running an instance of Windows Server software (loading it into memory and executing one or more of its instructions) customers must assign a Windows Server license to a physical server. Assignment/reassignment rules for original equipment manufacturer (OEM) licenses are different from Volume Licensing and retail license rights. With a license purchased with a server from an OEM, the Windows Server license is already assigned to that specific server, and lives and dies with that server. The OEM end customer is not allowed to reassign that OEM license to another server.

Windows Server is primarily licensed using a Server + CAL model or a Processor + CAL model. Windows Server Standard and Enterprise editions are licensed using the Server + CAL model, while Windows Server Datacenter and Windows Server for Itanium-Based Systems editions are licensed using the Processor + CAL model. Under both models, the CAL that accesses the instance of Windows Server must be equivalent or higher in version than the server being accessed. An exception to this rule was introduced with Windows Server 2008 and continued with Windows Server 2008 R2. Under that exception, customers must still license the appropriate CAL version to access the version of the server software running in each virtual operating system environment, but they are not required to upgrade their CALs based on the version of Windows Server that is running in the physical operating system environment. In this scenario, the Hyper-V server role must be the only role running in the physical operating system environment.

A Windows Server 2008 Client Access License (CAL) must be purchased for every user or device that accesses or uses the Windows Server 2008 or Windows Server 2008 R2 server software, except under the following circumstances:

For further information on Windows Server 2008 R2 please click here