title: C++ check if any user is logged in to windows 7
body: <p>I use psexec to run my app,
  Some of the tasks my app does should have a logged on user,
  so I want to check (from the app, not the server which runs the psexec)
  if there is a user which currently logged on. I couldn't find any api which retrieve this. My code is in c++.
  Any idea to check it?</p>