There is a documentation error in the Relnotes.htm file that is included with the Professional Developers Conference version of Microsoft Windows code named "Longhorn" Preview Release

This article discusses a preview release of a Microsoft product. The information in this article is provided as-is and is subject to change without notice.

No formal product support is available from Microsoft for this pre-release product. For information about how to obtain support for this preview release, see the documentation that is included with the preview product files.

SYMPTOMS
The Relnotes.htm file that is included with the Professional Developers Conference (PDC) version of Microsoft Windows code named "Longhorn" Preview Release includes a link to Microsoft Knowledge Base article 827662. The Relnotes.htm file states that this article contains the release notes for this preview release.
RESOLUTION
The release notes for Windows code named "Longhorn" Preview Release are contained in Microsoft Knowledge Base article 829967. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
829967 Release Notes for Microsoft Windows Code Named "Longhorn" Preview Release