Windows Server System:
Windows Server System, formerly known as .NET Enterprise Servers and before that as Microsoft Back Office, contains the flagship Windows Server 2003 operating system and Microsoft’s newest server-based applications. The goal is to offer ① a series of integrated components that provide a robust operations infrastructure (ISA Server, SMS, MOM, and Application Center), ② a reliable application infrastructure (SQL Server, BizTalk, Commerce Server, Content Management Server, Host Integration Server, and Speech Server), and ③ a flexible knowledge worker infrastructure (Exchange, SharePoint Portal Server, and Project Server) and to implement them on top of ④ a solid server platform (Windows Server 2003, Windows Small Business Server 2003, and Windows Storage Server 2003).
Microsoft Office System:
This is a rebranded and expanded packaging of Microsoft Office. It contains the traditional office offerings, such as Word, Excel, Access, PowerPoint, and Outlook. It also includes FrontPage, OneNote, Publisher, Project, Visio, and InfoPath. In addition, although it is designed as a desktop productivity suite, the Office System also includes two new server-side applications: Live Communications Server and Live Meeting.
参考：《Microsoft Exchange Server 2003 Distilled》ISBN: 0-321-24592-X