Broken or missing project templates in Visual Studio 2008 or 2005
After my last system restore, I got this annoying issue when I opened a VS solution with test projects and some other project types. This is basically becasue of the "broken templates" issue. I came across this post (Update: may be this for VS2010, or this for older versions, or this one for VS2012) that describes the problem and solution which in my case simply fixed running this command devenv /InstallVSTemplates from a Visual Studio command prompt with admin privs (for Vista).
In my case, that solved my problem. If you don;t have that luck then you may read all the above post and follow the rest of the steps.