Nowadays, security needs to be the #1 priority on Windows PCs, even those used at home. Here are 10 free tools you can use to increase the level of security on your home PCs.

Windows Firewall, Windows Update, User Account Control

Although Windows Firewall, Windows Update, and User Account Control (UAC) are built into many versions of Windows, I'm amazed by the number of PCs that have these three tools turned off. Also amazing is that some people pay for utilities that replicate what Windows Firewall and Windows Update do for free. In short, Windows Firewall helps you protect your computer by blocking unauthorized network connections. Windows Update ensures that your OS and Microsoft applications are updated with all the latest patches. UAC (in Windows Vista and later) helps distinguish between authorized and non-authorized changes or actions in your computer. For more information about these tools, see the Security & Safety web page.

Microsoft Security Essentials

Microsoft Security Essentials is not only free but also uses few resources. It guards against viruses, spyware, and other malware. An extra advantage is its "low-profile" approach to security: It notifies you only when it's really necessary.

McAfee SiteAdvisor

The McAfee SiteAdvisor browser plug-in makes it easy for you to identify the reputation of a website before you click the link. It's ideal when a page contains multiple links (such as a search engine's result page) and you aren't sure which one to trust. There's also a paid version that provides additional security features.

Secunia Personal Software Inspector

Secunia Personal Software Inspector will scan your disks and detect most (if not all) instances of outdated programs, DLLs, and ActiveX components, including Adobe Flash Player, Java, and Adobe Shockwave Player. In most cases, it will give you the option to automatically update them. I can't stress its usefulness enough!

Windows Virtual PC

Windows Virtual PC or another virtualization product can be an invaluable security tool when you need to run programs or visit websites you don't trust. In addition, you can use a virtualization product to create dedicated virtual machines (VMs) with minimal software installed on them just for connecting to sensitive sites, such as the site you use for online banking.

Enhanced Mitigation Experience Toolkit

Microsoft's Enhanced Mitigation Experience Toolkit (EMET) is a commonly misunderstood tool, even by its supporters. It can provide an additional layer of protection that can be useful for applications that are common targets for zero-day exploits, such as Microsoft Internet Explorer (IE), Adobe Reader, Adobe Flash Player, and Java. More and more of the technologies EMET leverages are finding their way to newer Windows versions, which makes EMET a useful tool especially for older OSs, such as Windows XP. Its latest version (EMET 3.0) also exposes some new features (such as configuration through a Group Policy Object -- GPO) that bring it a step closer to enterprise deployment.

Sandboxie

Sandboxie offers the capability to run a program in a sandbox when there's need to do so or even permanently. This means that the damage will be contained if the program gets compromised. It's useful when browsing less-trusted websites or opening untrusted documents, which makes Adobe Acrobat, Microsoft Office, and IE good candidates. The concept is similar to virtualization but Sandboxie is much less resource intensive and much more convenient, although not as powerful. Personal use of Sandboxie is permitted free of charge for as long as you want. There's also a paid version that removes the nag screen of the free version and provides some additional features you might appreciate.

VirusTotal

VirusTotal is a website that you can use when you're suspicious about the malicious nature of a file or URL. After you upload the file or provide the URL, this free service will check it against more than 40 different anti-malware products and present you with the results.

Create Your Own Line of Defense

Some of these tools can be repurposed and still stay within the "stay secure" concept. For example, Sandboxie can be used as an alternative to IE's InPrivate Browsing mode. However, none of the tools can be totally replaced by another. So, you should mix and match to create your own line of defense.