|Norton is just bloatware and does not really do a good job.|
You may want to try Avast Free:
and see what it finds Norton has left behind, be sure to do a bootscan on reboot and move all it finds to the chest.
If it recifies your problem and you decide to keep using it, be sure to use the Norton uninstaller from their website so that it cleans out all the Norton registry items or no other AV will work properly.
I have removed lots of Norton utilities in the past while and replaced them with Avast.
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