Sorry for being particularly stupid, and I probably haven't read nearly enough documentation on this yet, but I still can't work out how to get to Admin Authentication from the previous posts.

The Default Authentication extension has Enabled ticked in extension settings, the only other option there is Use Captcha.

Ideally I would like to enable Windows authentication, is that possible via this extension?

Les, to my understanding - DNN 5.x documentation is way off than the actual functionality. Documentation is not up-to-date at all. One has to play, experiment, and struggle to figure out what changes are made and where exactly are the control and check points. I am with you on this.

When you go to "Host->Extensions" you are able to see all the extensions, and also this is the place where you set the extensions for the entire DNN installation. While "Admin->Extensions" is the place where you set the "extension properties & options" for the specific portal.

Again, to my understanding, for integrated windows authentication, you will need to install "AD Authentication Provider" (Host->Extensions - scroll to bottom - on bottom right click "Install Available Extension" - then install "AD Authentication Provider").

Once you install AD Auth Provider - then you need to configure it to do this click "Admin->Extensions" then click on the "Edit Pencil Icon" next to AD Auth Provider and then configure it to work with your setup.

Me no expert on AD - so refer AD Auth Provider forum under "Authentication Providers" forums.

Hope that helps,

Good Luck,

Sincerely,
Sid