Windows 7 is the latest release of Microsoft Windows.  It's designed for faster and more reliable performance, so your PC just works the way you want it to.

 Windows Server 2008 R2 Standard is a robust and reliable foundation on which to develop, deliver, and manage rich user experiences and applications. Windows Server 2008 R2 Standard provides a secure network infrastructure and reduces costs while increasing technological flexibility and value within your organization.

The Operating System for Large-Scale Virtualization and Scale-Up Workloads

Windows Server 2008 R2 Enterprise is an optimal operating system for servers running applications such as networking, messaging, inventory, databases, and customer service systems