Just in case anyone was wondering, you're safe to install the service pack for Visual Studio 2005 on a machine that has the .NET Framework 3.0 Extensions and/or the "WPF/E" project templates. One thing to be aware of is that Visual Studio 2005 SP1 includes the web application project types which are required as a prerequisite for the "WPF/E" installation, and you're strongly encouraged to remove the add-in that I mentioned in step 5 of this post before installing SP1.