I had this problem with the same version a couple of days ago on a pristine, newly partitioned and formatted drive.?What worked for me was to set up a dummy User Account and log in as that user, then install - and the only other account was Administrator. (!)? This also fixed an identical problem with RoboHelp 7 installation.? Why it works, I don't know, but I found this solution on the Adobe Support site.
Jack
