If your internet provider doesn’t provide a free subscription to a major anti-virus / security suite here are some free options.

I know the first one (AVG) includes some email protection also if you still use local email (not web mail like hotmail, Gmail, yahoo mail, etc).

For your PC:
http://free.avg.com/
http://www.cloudantivirus.com/
http://www.avast.com/eng/download-avast-home.html
http://antivirus.comodo.com/

Online scanners that can be used in case you think your local anti-virus is missing something:
http://www.kaspersky.com/virusscanner
http://housecall.trendmicro.com/