Did you install the LockDown browser on your PC to take an exam online, that is the usual cause of this problem.
Click your Start Button, then just type cmd
On the resulting list, right click Command Prompt and select 'run as Administrator'
Paste each of these commands into Command one at a time and press Enter, wait for each command to complete, before running the next command, if you receive an error on any command, ignore that and continue to the next command.
reg delete "HKLM\Software\Microsoft\Windows\CurrentVersion\Policies" /f
reg delete "HKLM\Software\Microsoft\WindowsSelfHost" /f
reg delete "HKLM\Software\Policies" /f
reg delete "HKLM\Software\WOW6432Node\Microsoft\Policies" /f
reg delete "HKLM\Software\WOW6432Node\Microsoft\Windows\CurrentVersion\Policies" /f
reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies" /f
reg delete "HKCU\Software\Microsoft\WindowsSelfHost" /f
reg delete "HKCU\Software\Policies" /f
reg delete "HKLM\Software\Microsoft\Policies" /f
Then, close Command Prompt and restart (not shut down) your PC