Ok I've done a bit more testing as this is what I have so far ..
Did a complete reinstall as follows:
copied the "forum" folder to the web server
In IIS admin set the "directory Security" for that folder to Integrated Authemtication only
Setup a new DB and ran the initial setup as per instructions
Logged on to the system - this happen as an AD user.
changed the last bit in the address from "/default.asp" to "/admin.asp"
logged in using the default administrator account and password
Went to "membership admin", clicked on the AD user account that had been automatically created (as "newbie" ) and then clicked on "Edit this members forum settings"
No option is available for "Admin and Moderator" functions - I'm pretty sure that when I click on the username and it pops up the new window for editing it's authenticating me as the AD user who is a "newbie" not the admin account
I then did a bit more fiddling - I went into the Database and changed the group membership for the AD account to "1" effectively making that account an admin account - I then logged on as the default administrator account (using /admin.asp) and checked that the AD user was an administrator.
The I logged on as the user by just opening a new browser and I then had the link to the Admin function in the top options, but when I click on it it asks for a password (the username cannot be changed) and it's not the password from AD so there's no way to go any further...
Is this something that can definitely be done? To have an AD user be an administrator for the forums?
thanks
Barry