Application with other user name and password login -How-?

[MrWoff]

i can create a user with

                DirectoryEntry AD = new DirectoryEntry("WinNT://" + Environment.MachineName + ",computer");
                AD.AuthenticationType = AuthenticationTypes.Anonymous;
                DirectoryEntry ATatorithät = AD.Children.Add("ATUserP3", "user");
                ATatorithät.Invoke("SetPassword", new object[] { "ATuser" });
                ATatorithät.Invoke("Put", new object[] { "Description", "User from safe.exe" });
                ATatorithät.CommitChanges();

how can my application login with this user?