After developing a WPF application without Source Control, I decided to add the solution to TFS.
After doing so whenever I opened the main window.xaml file in Design
If you wish to keep Power Commands for Visual Studio 2008 installed, see this workaround here:
PowerCommands crashing VS2008 SP1
But basically:
a work around which is a simple modification to the devenv.exe.config file.
This will exist in (64 bit systems) C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE
Or (32 bit systems) C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE
Add this XML token to the dependentAssembly list. They had me add it after the office one, but im not sure if that matters.
This worked nicely for me.