I am not from Laminar Research; just a flight simmer from down under.
Like you I also use a boxed set from Aerosoft and have the same concerns for the ongoing security for disk 1.
If you know how to create a replacement/substitute ISO disc for XP disc 1, from XP11 disc 1 then good luck. I don't .
Because Aerosoft is Licenced to sell the disc version Laminar Research does have a replacement for disc 1 process. You need to make direct contact with Laminar at firstname.lastname@example.org There will be a small charge for the disc and postage.