Windows 10 Windows 10 Start Button Multiple Computers

This is a story involving multiple computers. Computer 1 ("C1"), was upgraded to Windows 10 from Windows 7 several months and never had any problems. Computer 2 ("C2") was upgraded, worked for a day and then the dreaded Start Button "Critical Error" message began. It seemed Norton related so I uninstalled Norton and reinstalled Norton up to the point where the second patch is requested so before that point the Windows 10 Start Button works but before that, the Start Button doesn't then after the installation of the second patch it doesn't again. I talk to Norton and Norton blames Windows, go figure.

In further attempt to resolve this issue on C2, I began following some advice given at the BT webpage where there is a post describing four ways to fix this problem and the only thing that worked was creating a new account. That worked for several days on C2 but then a new development occurred as the first account in C2 somehow communicated some settings to C1 as the background picture transferred over without my changing any settings. A couple days later, the C2 account 2 Start Button also began to stop functioning while simultaneously the Start Button on C1 ceased functioning.

This bug appears to have something to be involved with the maintenance of the account settings.

Your help would be much appreciated.