During the last 4 months numerous attempts to upgrade my laptop from Win 8.1 to Win 10 all ended in error code 80070005.
I checked administrator rights, performed Clean boot, ran Fixit and whatever people propose in this thread and in Microsoft support forums, but nothing helped.
Finally I decided to completely remove Norton security via my Norton login. After one more reboot followed by Fixit the Win 10 upgrade installed!. Everything works fine now and I could reinstall my copy of Norton Security via the Norton login.
Apparently Norton Security leaves som kind of blockage even when disabled and even after Clean boot.