Microsoft recommends that you use the Office Update site to determine if your computer requires this update before installing it.
This update addresses a problem where Visio 2003 overwrites some registry settings for msxml2.dll and msxml3.dll. The problem may prevent applications utilizing these files from running properly. For more information on this update, see the Microsoft Knowledge Base article (831925) Overview of the Visio 2003 Update: KB831925.