A website that was working fine is now asking for username and password.
The security settings HAVE not been changed.
That being said, enable anonymous access is checked with the proper account, which is the same account on the folder settings that has full access. Integrated Windows authentication is also checked.
Why all of a sudden is the site asking for credentials.
The ONLY modification was changing the app pools and the .NET version, which since have been changed back to its original settings.