Bvs1216 uses Microsoft Security Essentials. He asked the Answer Line forum if he needs to supplement it for additional protection.
That all depends on what kind of supplement you're looking for. You only need one antivirus program, and Microsoft Security Essentials fills that role. But an antivirus program isn't the only kind of security software you may need.
Don't be misled by the term antivirus program. These programs don't just protect you from viruses (which, technically speaking, are passé, anyway). They protect you from Trojans, worms, spyware, rootkits, and all sorts of malware. As the term is generally used, an antivirus program is software that loads automatically when you boot, then stays in the background, protecting you against malware in real time.
But no software is perfect, so it's a good idea every week or two to scan for malware with another program. But you don't want another antivirus program; two of these running in the background at all times, doing the same job, is asking for trouble. You need an on-demand malware scanner--a program that only runs when you launch it and scans only when you ask it to. I recommend either SUPERAntiSpyware or Malwarebytes' Anti-Malware, or both.
You also need a firewall that can check for suspicious packages going in and out of your computer. Windows has its own firewall, but Windows 7 is the first version where I actually felt I could trust it. If you're using XP or Vista, you might want to consider the Comodo Firewall.
Read the original forum discussion.
Contributing Editor Lincoln Spector writes about technology and cinema. Email your tech questions to him at firstname.lastname@example.org, or post them to a community of helpful folks on the PCW Answer Line forum. Follow Lincoln on Twitter, or subscribe to the Answer Line newsletter, e-mailed weekly.