Numerous users reported both here and on Microsoft sites that after upgrading to WIN 10 their laptops became unusable, due to a rapid flicker after log-in that left them with no functionality except the Task Manager.
In my case, the problem was not solved by creating a 'test" user with admin privileges in CMD and then logging in as such, but flickering slowed down enough so that the cause could be detected by watching the processes running on the task manager:
Norton swamps users with notices that 360 Premium is WIN10 compatible. This may be so, but is only part of the truth. For those who like me previously had Norton One/ Norton 360, the program was updated some time ago to Norton 360 Premium, BUT the Norton One directory was not uninstalled. It is also not uninstalled by the current Norton uninstall program. This directory contains executable files that trigger a MS error report and set in motion an endless loop between the two, with resulting screen flickering.
My solution was simple, but time consuming: reinstalled backup image of WIN7 from external media, ran Norton uninstall, manually deleted Norton One directory, checked Registry with CCleaner and re-installed WIN10. No more problems.
Symantec should make this public or provide a patch that uninstalls all Norton One content conflicting with WIN10.