[Update: This program is no longer available.]
Do you write managed apps or components? Then you should run them on a special edition of the .NET Framework 2.0 Beta 1. With this, you can now give Microsoft direct feedback on what portions of the .NET Framework and Win32 you're dependent on! This will help us maintain compatibility with future releases of the .NET Framework and prioritize our testing on the functionality you care about most. We'll even send you info when future drops of the .NET Framework are released that will describe how .NET Framework code changes post-Beta 1 might impact your applications and components.
You can download this special edition here: http://www.microsoft.com/downloads/details.aspx?FamilyId=CC36F05E-2050-4E54-B460-E99E50156712&displaylang=en
Be sure to read through the documentation (which is a separate link on the download page) to help you install and use it. For example, on Windows XP the installation won't succeed unless you've got SP2. And please don't hesitate to contact me if you have any questions or issues.