Did you have a look on the Microsoft Site? http://www.microsoft.com/windowsserver2003 I'd say it would tell you there and my best guess is that it will run on the Itanium and Itanium 2 only. It's specially designed to run on them processors and you'll need the normal 32-bit version for the other chips.
I use Microsoft Visual Basic 2005. (Therefore, most code samples I provide will be based around the .NET Framework v2.0, unless otherwise specified)
* Important: The 64-bit versions of Windows Server 2003, Enterprise Edition and Windows Server 2003, Datacenter Edition are only compatible with 64-bit Intel Itanium-based systems. They cannot be successfully installed on 32-bit systems.