2
what you set in preferences is which module it will go to, when you type in your site's URL in the browser address bar.
How do you log in? With the login block or the user.php page? When you log in with the login block, it will go to the same page you were at before the login. If you try as anonymous to go to a module you don't have permissions for, it will redirect you to user.php for the login form and after submissal, it will go back to user.php which redirects to userinfo.php?uid=[yourID] for logged-in users.
Hope this clarifies.