Microsoft has made a new trial VHD available for Windows Server 2008 R2 Enterprise Edition 64bit.
From the overview
The Microsoft VHD Test Drive Program provides customers a flexible, extensible and supported evaluation experience requiring minimal hardware and IT overhead. You can access the catalogue of pre-configured Microsoft solutions in VHD format for test, evaluation, demonstration, training & education and proof of concept from www.microsoft.com/vhd.
This download helps you evaluate the new features of Windows Server 2008 R2. You’ll have the opportunity to try new and improved features and functionality of Windows Server 2008 R2 free for 180 days. Windows Server 2008 R2 builds on the award-winning foundation of Windows Server 2008, expanding existing technology and adding new features to enable IT professionals to increase the reliability and flexibility of their server infrastructures. New virtualization tools, Web resources, management enhancements, and exciting Windows 7 integration help save time, reduce costs, and provide a platform for a dynamic and efficiently managed data centre. Powerful tools such as Internet Information Services (IIS) version 7.5, updated Server Manager and Hyper-V platforms and Windows PowerShell version 2.0 combine to give customers greater control, increased efficiency and the ability to react to front-line business needs faster than ever before. To find out more about Windows Server 2008 R2, please visit the product homepage. Please note that this product is available for evaluation purposes only and should not be used in a production environment.
This is a preconfigured virtual machine set contained within the Virtual Hard Disk (VHD) format. Windows Server 2008 Hyper-V, Microsoft Hyper-V Server 2008, or the R2 versions of these products is required to use this virtual machine. Please refer to the system requirements section for more details.
You will need Windows Server 2008 Hyper-V to run this VHD. Also because its 64bit you will need 64bit capable processors (Intel64 or AMD64 extensions) with hardware virtualisation (AMD-V or Intel-VT) and DEP.
Download from here