Help after reading other posts I am suffering the same problem ....Windows downloaded its big update 2 days ago and I noticed yesterday that Norton is turned off and Windows Defender is now being used(never used it before)...Norton has been working for the past 4 yrs....I can get to the page to turn off Windows Defender...both the anti-virus and the firewall....and it gives me the option of turning Norton on but nothing happens....One page that shows both Norton and Windows Anti Virus.. has left Norton in a grey area but it will let me turn Defender back on ....Norton.. states error 8504.101...and offers to download a patch that require a restart but after restarting nothing has changed.....Also Norton will not start from Desktop......HELP