If you are using Discountasp.net as your website provider, disable WebDAV. Apparently WebDAV is tied to Windows authentication, and for me at least, caused my site using forms authentication to fail.

Also, you probably need to get IIS7 Manager installed locally to set the IIS authentication to Anonymous and Forms. Windows authentication won't show up up in this filter, but as mentioned above can be enabled/disabled by setting the WebDAV property in the Discountasp.net control panel for IIS.