A: 

You should be able to find the assembly under the ".NET" list of assemblies in the "Add Reference" dialog.

Nader Shirazie
+4  A: 

You should be able to find it in the "Add Reference" dialog in the .Net tab.

If not, the Microsoft.VisualStudio.DebuggerVisualizers.dll lives in the Common7\IDE\PublicAssemblies subdirectory of Visual Studio's installation directory. You could add it manually from there.

adrianbanks
and where does it come from?
Svish
Apparently, it ships with Visual Studio. It might be that you turned off a feature when you installed Visual Studio which has caused it to not be present.
adrianbanks
hm... will have to try reinstall it or something then I guess...
Svish