Microsoft released Windows Server 2008 R2 . You might want to use this latest Windows Server operating system for the following reasons according to Microsoft:

Powerful Hardware and Scaling Features
Reduced power consumption
Hyper-V in Windows Server 2008 R2 – Virtualization improvements
Reduced Desktop Costs with VDI – Improvements in virtualized resources and better integration with local peripheral hardware as well as powerful new virtual management features
Easier and More Efficient Server Management
Managing Data Not just Managing Storage
Ubiquitous Remote Access
Improved Branch Office Performance and Management
Simplified Management for SMBs
The Strongest Web and Application Server To Date

Windows Server 2008 R2 will be available in the following versions:

Windows Server 2008 R2 Foundation
Windows Server 2008 R2 Standard
Windows Server 2008 R2 Enterprise
Windows Server 2008 R2 Datacenter
Windows Web Server 2008 R2
Windows HPC Server 2008 R2
Windows Server 2008 R2 Itanium-Based Systems

Previous versions of Windows Server include: 2008, 2003, 2000, and NT.

For further information please visit:

http://www.microsoft.com/windowsserver2008/en/us/default.aspx

This information is subject to change. Please refer to Microsoft documentation for full details.