As a number of folks have mentioned, it's time for you to give it a shot: http://technet.microsoft.com/en-us/evalcenter/cc184869.aspx

Here are some details:

Brief Description Public Preview Software – Release Candidate 0 Windows Essential Business Sever 2008 is an integrated and affordable solution that offers the Microsoft software midsize businesses require - preconfigured, integrated and manageable from a single administrative console, and at a significant discount compared to standalone products.

Quick Details

• Version: 6.0 Date
• Published: 5/12/2008
• Language: English
• Download Size: 11092.1 MB

Overview Designed and priced for midsize businesses, Windows Essential Business Server 2008 simplifies your daily activities with a Centralized Administration Console that gives you a single point of access to your IT environment. Windows Essential Business Server 2008 also provides an integrated and predictable platform, allowing you to view, deploy, manage, and administer third-party applications from one starting point.

System Requirements

Supported Operating Systems: Windows Server 2008

Notes: Windows Essential Business Server 2008 Standard Edition is only available as a 64-bit operating system As this is not final release code, you may not install the software in a live operating environment

Processors

• Systems with Single Core CPU - x64 with a 2.5 GHz minimum clock speed
• Systems with a Multi Core CPU - x64 with a 1.5 GHz minimum clock speed
• Systems with Multiple Physical CPUs - x64 with a 1.5 GHz minimum clock speed

RAM

• Management Server - 4 GB of RAM
• Security Server - 2 GB of RAM
• Messaging Server - 4 GB of RAM

Hard Disk Drives

• Operating System Drive Partition – Minimum of 40 GB of free disk space
• Application Data Drive Partition – Minimum of 20 GB of free disk space