Hi Chris,
Thanks for this and before I saw your latest message I did try the fixit solution again, several times but each time got an error message 80072EE2. I did notice that the fixit said it was 64 bit and mine is 32 bit. I searched for a 32 bit fixit but couldn't find one.
So I created a new user account but when I tried to log on got the message "The user profile service failed the login. User profile cannot be loaded.
So I spent some time trying various remedies for this from the microsoft site and elsewhere, including another fixit solution. Deleted the new user account and created a new one two more times, but with the same result.
I found an Air folder in the Public user account and deleted that.
I uninstalled some recently installed software I thought might be the cause and tried several more times to install Air but with the same outcome.
I also tried to install after a clean boot but again no joy.
Sorry to be such a pain 