If you practice basic computer security measures the chances of your machine becoming infected with a virus is almost nil.

Don't open emails from people you don't know, don't open email attachments even from people you do know, don't install programs from other than trusted sources, don't click strange links, keep your software updated, stay away from porn sites (though I realize that's not a problem for you), etc.

I use Microsoft Security Essentials and Malwarebytes Anti-Malware on my machines and haven't had a virus or malware infection in years.