All I use is Free Avast and Windows Firewall, and I do online Banking and and use my CC. Why the need for all the other stuff is beyond me, I have never had a Virus. But there again I do not use a PS3 or Do Games etc, and take care opening E-Mails and how I surf the Web.
Been using PC from Win95 days when I spent lots of Nights reloading Windows and software after, trying Cover Disc's. I finally found out the Problem
Provided you observe some common-sense precautions
you'll be perfectly safe using your card for online purchases.
The first thing to do is forget the idea that your own money is involved - you are not spending that, you're spending VISA's money. You obviously have to repay it, but provided you've taken reasonable steps to safeguard your card details the card provider will bear the consequences if something goes wrong.
You'll hear people saying 'I don't use my card online because it's not safe', but that's not the point; online purchasing is as safe, if not safer than handing your card to a waitress in a restaurant, or using it in a petrol station.
As has been pointed out, secure servers (those that have 'https' in front of the address) establish a safe link with your computer for the duration of the transaction, and as long as you check to make sure that you see the 'https' and a small padlock symbol in your browser you'll be as safe online as you would be in a shop. If something goes wrong, let your card provider know about it immediately, and they'll take the strain.