MIcrosoft is ending support.. I do not know if Norton is ending support.
The major issue is that nearlly every day a new vunerability is found in windows so Microsoft issues bandaids every "patch tuesday" I got over 20 of 'em last time. However I do not rely on MS to provide my security, I have 3rd party Anti Mal-ware and 3rd party Firewalls. (And no I won't tell you which ones)
I will say this.. When the first malware (A virus as I recall but that recall may be faulty) hit the net two companies were johnny on the spot with anti-virus software.. Norton and McAffey, others came shortly after. I went with someone else at that time (And never regretted it) F-Prot, which alas I can no longer use. (It does not support my current OS).
I often wondered if the commercial companies were "Seeding the market" by hiring folks to write virus programs.
Turns out.. I am told by one of my instructors.... One of them did.
Now my instructor personally knows the founder of the OTHER company and says he'd never do such a thing...(I have no reason to doubt him) but it is interesting.
This is one of the reasons I choose to use FREE anti-virus programs.