My vote: You.
No really; the best anti-virus and internet security is the user, so long as they know what they're doing (sadly, thats probably the reason why most AV and IS companies exist - people have no idea what they're doing XD )
But if you insist, nod32 + avg + some form of firewall (heck, even the windows default one isn't half bad when put together with a decent AV). Just remember: the best IS/AV you'll find is you. Don't download from untrustworthy sources, don't click attachments in emails you didn't expect attachments in, the works. Doesn't hurt to have something as an emergency safety net though