For anyone who knows anything about computers, I recommend NOT using desktop security that runs all the time (AVG, McAfee, Norton, etc).
If you're one those that just clicks blindly yes to everything that appears on the screen, or really believes that you are in fact the one millionth visitor to this site, try saran wrapping your internet connection to keep the viruses out.
Before you call me an idiot, understand the levels of protection already provided for you by your operating systems manufacturer.
Windows Security Center (automatic updates enabled) + a properly set up firewall should keep MOST if not all malware from your computer. Microsoft/Apple/Google spend billions on security for your machines, they are far superior to those offered by third parties. Most desktop suites I find act almost as malware as they constantly check for breaches, which in turn slows down your computers performance.
If you feel that you might have caught something like the NSMB ad virus, a scanner will be sufficient to clean it up. Just be careful, many malware companies are creating fake "scanners" which are really just malware themselves.
Recommended scanners include:
Windows Defender (built into Xp, Vista, 7)
MalwareBytes (what I use)
AdAware
Windows Security Essentials
Have fun out there kiddies, if it looks to good to be true, don't click on it.