If you want to install the "Visual Studio 2005 extensions for .NET Framework 3.0 (WCF & WPF), November 2006 CTP" *after* you have installed .NET 3.0 Service Pack 1 you will receive a message saying
"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."
In this you either need to
1) uninstall 3.0sp1, reinstall 3.0, install vsexwfx, reinstall 3.0sp1
2) or add the following value to your registry
"DisplayName"="Microsoft .NET Framework 3.0"