ASP disables itself in IIS7.5 Win Server 2008 R2

ASP disables itself in IIS7.5 Win Server 2008 R2

I've just moved an asp web site to another box. Both have Windows 2008 R2 with IIS7.5 and over 2GB of RAM.
I've got the site working with ASP after some difficulty. Naturally I changed this line in the \inetpub\temp\apppools\.config file:
        <section name="asp" overrideModeDefault="Allow" />
However each time I save / change the settings in IIS Manager the above line changes from 'Allow' back to 'Deny'! I have to manually change it back. The same happens if the server reboots.
So IIS is getting the 'Deny' setting from somewhere - presumably the applicationhost.config file - but where?
In applicationhost.config:
    <sectionGroup name="system.webServer">
        <section name="asp" overrideModeDefault="Allow" />
Here's the applicationhost.config | Location section for the site:
<location path=<site name> >
  <system.webServer>
        <security>
            <authentication>
                <anonymousAuthentication userName="" />
            </authentication>
        </security>
    </system.webServer>
</location>
So I'm plum out of ideas. Is there somewhere other than applicationhost.config that IIS uses? Can't help feeling it's something really simple but what?
Thanks in advance ...