Tried Overtop of 2015, then rebooted into Safe Mode, and did uninstall, then rebooted again and ran Avast clear, tried again, failed installing 2016 beta 1 and now beta 2 on Windows 10 Desktop, Laptop XP had the same issue, but couldn't generate support file, errored same as Desktop,
Then Laptop had trouble booting, so ended up doing a whole reformat on Laptop, and then installed it again, and worked on that one, Might try Bob3160's steps again on Desktop early tomorrow or later tonight, and see if it works any better, This is kinda major issue that needs solved before less tech savy users are updating there Computers to version 2016.