Microsoft Knowledge Base Article 889100 contains the following summary:
This article tells how to obtain Microsoft Windows Server 2003 Service Pack 1 (SP1).
Microsoft Windows Server 2003 updates are distributed in service packs. Service packs keep the product current. Service packs include updates, system administration tools, drivers, and additional components. These are conveniently bundled for easy downloading. Service packs are cumulative. Each new service pack contains all the fixes that are included in previous service packs, and any new fixes. You do not have to install a previous service pack before you install the latest service pack.
Note Beta versions of software, such as Windows Server 2003 Service Pack 1 (SP1), are intended only for installation in a test environment. We advise against installing and evaluating beta software on any production computers.
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