set the default outlook address book for all users
 

I know I have done this before a few years back in another site - but
I cant remember how.
We need to set the default lookup address book for all our OL2k3 users
to specific lookup order. I know they could each do this manually but
we have 2300+ users and the support overhead would be huge.

We want to make a custom defined AB we have created the First place
that is searched, rather than the GAL.
I am pretty sure that last time I did it by pushing out an HKCU
registry setting through a GPO - but now I cant remember how :)

Anyone got any ideas.
Al.