I was asked the question, at a recent TechNet event, whether the Central Store for the new ADMX admin template files requires Windows Server 2008. I said it did not and that I would post some info in my blog to show how the Central Store is created.
From the FAQ at : http://technet2.microsoft.com/windowsserver/en/technologies/featured/gp/faq.mspx#EJF
Q. What is the central store?
A. The central store is a folder created on the SYSVOL of an Active Directory domain controller and provides a single centralized storage location for ADMX and ADML files for the domain. You can create a central store on a domain controller running Windows Server 2003 R2, Windows Server 2003 SP1, or Windows 2000 Server. The creation of the central store does not require Windows Server Code Name "Longhorn."
More information: Managing Group Policy ADMX Files Step-by-Step Guide
And this link is to a KB article that specifically walks through creating a central store: http://support.microsoft.com/kb/929841