JSI Tip 10334. MMC 3.0 update is available for Windows Server 2003 and for Windows XP.

Microsoft Knowledge Base Article 907265 contains the following summary:

This article discusses an update to Microsoft Windows Server 2003 and to Microsoft Windows XP that includes Microsoft Management Console (MMC) 3.0. MMC 3.0 hosts a variety of operating system and third-party administrative tools.

Note MMC 3.0 is included in Microsoft Windows Server 2003 R2 and in Microsoft Windows Vista.