avast! 4 Home Edition
This slick, skinnable antivirus app looks like a high-tech media player, but it's really a virus fighter. It scans files on demand and on access, including e-mail attachments. No scheduling—you have to pay for that—but it can send a warning on detecting malware. A boot-time scan option removes ­tenacious malware. And it's 64-bit compatible.—Neil J. Rubenking

AVG Anti-Virus Free Edition
This program splits its user interface between Control Center and Test Center, which can be a bit confusing. But it does what an antivirus app should: It scans files on access, on demand, and on schedule. It also scans e-mail, both incoming and outgoing. According to Grisoft, it's totally Vista-ready.—NJR

Dodge Bad Guys

Comodo Firewall
The new kick-ass choice for free firewall protection, Comodo Firewall keeps hackers out and keeps ­unauthorized programs from accessing the Internet, even tricky ones that sneak around normal ­program control. And it resists being forcibly terminated. It works as well as all but the very best for-pay firewalls.—NJR

McAfee SiteAdvisor
McAfee's back-end servers crawl the Web to evaluate sites. Does the site host malicious software? Will it spam you? Are there exploits in the code? If SiteAdvisor red-flags a site you're visiting, get outta there! It evaluates all the links from Google and popular search engines so that you need never find yourself on a red-flagged site.—NJR

SpyCatcher Express
When we last tested it, Tenebril's SpyCatcher did very well both at cleaning out spyware and at preventing further infestation. The free SpyCatcher Express edition has almost all the features found in the paid version. It lacks antiphishing and a few high-end tools, and you have to check for updates manually, but it does the job.—NJR

StartupMonitor alerts you to programs that try to install themselves whenever you boot up Windows. Unlike most similar utilities, this one is unobtrusive and won't interfere with program installations that reboot automatically.—Ed Mendelson

SuperStorm Freeware
SuperStorm Freeware protects a sensitive file (up to 200KB) by encrypting it and hiding it inside a JPEG image, and then securely deleting the original. A for-pay Pro edition has no size limit and can encrypt with a user-defined password. SuperStorm can extract anything hidden by the Pro edition, and it uses a simple drag-and-drop interface.—NJR

Windows Defender
Microsoft bought Windows Defender's technology about two years ago, but the software colossus doesn't seem to have done much with it. The product's ability to remove entrenched spyware is mediocre, and it's not a lot better at keeping spyware out of a clean system. But it's free and built into OneCare and Vista, so use its on-demand scanner for a "second opinion."—NJR

The venerable ZoneAlarm doesn't have all the features of ZoneAlarm Pro's firewall. Its program control asks you whether to allow programs rather than consulting the SmartDefense Advisor database. It doesn't have the component control or OSFirewall features, so it won't block "leak test" techniques. But it's tough as nails; malware can't disable it.—NJR