You may get an install error when installing the Visual Studio 2005 extensions for .NET Framework 3.0 (WCF & WPF), November 2006 CTP:

"Setup has detected that a prerequisite is missing.  To use Visual Studio 2005 extensions for .NET Framework 3.0 (WCF & WPF), November 2006 CTP you must have the .NET Framework 3.0 runtime installed.  Please install the .NET Framework 3.0 runtime and restart setup."

This happens if you have .Net 3.0 Service pack 1 already installed.  One workaround is to add the following to your machine’s registry:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{15095BF3-A3D7-4DDF-B193-3A496881E003}]

“DisplayName"="Microsoft .NET Framework 3.0"

When you run the installer again it might complain (twice) about the MSDN documentation not being present, but just continue and the install should complete.

Robert Stam also came up with this workaround:

msiexec /i vsextwfx.msi WRC_INSTALLED_OVERRIDE=1

It requires you to open a Command window and navigate to the directory where vsextwfx.msi is located, but has the advantage of not requiring you to edit the registry.

Note that this CTP version will not be replaced by another release, you are expected to move on to Visual Studio 2008.