Basically I want to build a web app that will try windows authentication and if authentication fails then will provide the user with a login form ?
I do not want to have different web apps for different authentication modes.
Is this possible ? Did I missed some points about this ?
You could go into your IIS Error Pages settings and change the various target pages for the 401 error to point to a Windows Forms login page. That way, then the user bails out/fails for the three requested authentication attempts it redirects to another page.
You could set up more than one virtual directory that points to the same folder. One vdir uses forms auth and the other using integrated.