Microsoft Knowledge Base Article 918884 contains the following summary and introduction:

SUMMARY

This article describes how to upgrade to Microsoft Windows Vista Beta 2 from an earlier version of Microsoft Windows and how to perform a clean installation of Microsoft Windows Vista Beta 2. To upgrade to Windows Vista Beta 2, the operating system that is currently installed on the computer must be supported in the upgrade path to Windows Vista Beta 2. This article lists the operating system requirements to upgrade to Vista Beta 2. This article also lists some methods that you can use to troubleshoot scenarios where you receive an "Upgrade has been disabled" message when you try to upgrade to Windows Vista Beta 2. Additionally, this article describes two methods that you can use to start the Setup program to perform a clean installation of Windows Vista Beta 2.

INTRODUCTION

This article contains information about how to upgrade to Windows Vista Beta 2 from an earlier version of Windows and how to perform a clean installation of Windows Vista Beta 2. The information in this article applies only to Windows Vista Beta 2 and does not apply to other versions of Windows Vista.