I have tried many of the paid virus scanners and found that missed a lot of the viruses and worms. Some one told me about AVG available free from https://grisoft.com so I set out to try it.
I now have been using it for years and it is still free. If it ever went to pay I would purchase it.
I can set it to do automatic updates at a certain time and I have mine set for every 3 days. It is very important to keep any virus scanner updated at all times. You can manually run a full scan anytime or you can also set it to run the test at a given time you choose.
You get a little icon in your system tray and can access all features from there.
The other day I had gotten an e-mail that was infected and the program would not update so I went into the settings and unchecked the box that says check for an Internet connection which keeps people from getting in so easy.
It then updated fine and I was able to get rid of the virus in a few minutes time.
I feel safe with this program, it has never crashed my system and it has never not caught a virus that came through.
Always use precautions with any anti-virus. Do not open attachments or mail with strange subject headings or the words click here and so on. Only open mail from people and sites you know.
Remember too that a friend could send an attachment and that file could be infected without them knowing it so I never open attachments.
Also most service providers here now have a virus catcher on them and it will alert you and not show you the mail. You can never be too safe.
Some precautions and AVG will keep your computer from harm and running smoothly for many years.