A LOT more than you want to know.
The only way to prevent viruses, trojan horses, etc. altogether is never to access the internet, which pretty much prevents all the activities you've listed.
Plus you would have to prevent the use of any USB memory sticks from external sources, too.
Bottom line?
Find out if your Internet Provider furnishes an antivirus protection suite upon request.
You shouldn't ignore critical Windows updates; that's just asking for it.
Just opening the wrong email could ruin your entire month.
Thanks for your reply.
I have AVG and I NEVER open any email where I do not know the sender. Memory sticks are a mystery to me so I do not use them. I live alone and no one has access but me.
Is there any way I can tell if these “critical” updates will alter the way I have my computer screen set up as has happened when I allowed them to up date automatically