You work as a Software Developer for ABC Inc. The company uses Visual Studio .NET 2008 as its application development platform. You create an ASP.NET Web application using .NET Framework 3.5. The application uses Forms authentication. Your company uses Active Directory.

You need to modify the application to enable users to make use of their existing Active Directory account to access the application through the Internet. You are required to ensure that the application must be modified with the least amount of user interface changes, cost, and development effort. What will you do to accomplish this?