Hey. I've noticed that there are tons of people with this issue, not necissarily with the SDK but with the FSX Setup. I'm one of them, however, your solution seems to work for everyone - except me. I 'unlocked' the "superadmin" account but I still get 1628 when I try to install FSX. Any ideas?
PS. Fixed it. I ran it in the super admin account, and I found another post on a forum which required me to run iDriver, iDriver2 and iDriverT as admin.