Works in: XP, Vista, 7 Windows 7 comes equipped with some solid security tools, including a robust firewall and the spyware-blocking Windows Defender. On top of that, you need a good antivirus program, one that works quietly in the background and won't bog down your system. provides real-time protection against viruses and other kinds of malware, and its performance impact is negligible; PCWorld security guru Erik Larkin says it "holds its own" against other . Sounds like a fine alternative to paying an annual fee for virus protection.

Works in: XP, Vista, 7 The seemingly innocent act of clicking a link--even one that's at the top of a Google search-results page--can result in "" infecting your PC. Scary, right? But how do you know whether a link is safe to click? Try , a browser add-on that will warn you of unsafe sites.

Specifically, the plug-in adds color-coded icons to each link that your search engine produces: green for safe, yellow for risky, and red for dangerous. You can also right-click any link, such as one that appears in an online forum, and choose View WOT scorecard to perform a manual safety check.

WOT is free, and available for both Firefox and Internet Explorer. Although its rating icons add a little clutter to some Web pages, we recommend it very highly for anyone concerned about security.