I hope I may have some useful news.
(.... BTW what's that previous post about? Is someone trying to shift some software?)
Mine It is not yet a solution - but it's another clue which may help us all move just one inch or two closer to a positive result.
Well, sad to say, I have had exactly the same issue.
So I switched machines - BUT still to the same OS (i.e Win 7/64, installed with the very same disc in fact).
Unlike the Dell laptop upon which I struggled for days with this infuriating issue - much to my surprise the Win 10 setup file ran immediately with no problem at all ! (??)
So it must be something specific to the Dell machine hardware side, or (much more likely) the software and the way I have it configured (maybe something in Group Policy I have locked down?)
In terms of what is at fault, what is now eliminated from the list of suspects is .....
A. Win 7 itself, and
B. The Win 10 media (because the same problem arises when using a Win 8 setup.exe)
But ultimately, I don't really want the snooping, invasive, prying Win 10 on the machine upon which it will quite happily install. I want it on the machine that won't yet accept it (from sources/setup.exe). because that is not going to go online, other than to activate.
So the next move is to try to get XP (in dual boot) onto the problem machine and to see if I can run Win 10 setup from within that OS. ( But I doubt it.)
So, I personally feel a little nearer to solving the crime, but sorry for no solution yet.
Maybe after all these months you have some further info too ??
Please post if you have.
Regards