Antivirus software doesn't check all threats. Just known worms, trojans and viruses. It doesn't worry about spyware. Spyware is stuff that watches you and then send observations somewhere on the net. What it watches may range from which websites you visit to which keys you press when you are doing your banking online. If you want to keep safe online make sure you have something that keeps the Spyware out. I use Spybot S&D. S&D stands for Search and Destory. It's good. It's easy to use. It's regularly updated and it doesn't cost you a cent. Those are qualities I like in my software. In that order.
So all you Windows XP and Windows Vista users out there, you have a firewall. It's built into Windows and is usually turned on by default. Some of you may use other firewalls. If you have an nVidia chipset motherboard, you may have the nVidia Network Access Manager software or others like ZoneAlarm.
Everyone should have antivirus. Again, there are plenty of choices. Mine is Avast! but plenty of people will swear by AVG and others will insist on buying Nortons or McAfee.
And then there's the Anti-Spyware. Microsoft make a free anti-spyware package called Windows Defender. Whatever. Spybot is good, easy, free and up-to-date. There are others, both free and commercial.
So protect yourself.
And make sure that your windows is up to date.
Start => All Programs => Windows Update
Be safe online.