Over the last few years, anti-malware software has become increasingly costly. But believe it or not, there are still ways to protect your computer for free. In this article, I will list 10 free utilities you can use to either prevent malware infections or to help clean up the mess once a PC becomes infected.

Note: This article is also available as a PDF download.

1: AVG Anti-Virus Free Edition 2011

I have been using AVG’s free antivirus product for a few years now, and although it isn’t perfect, it seems to be at least as good as most of the commercial anti-malware products. AVG’s free edition provides basic protection against viruses and spyware, but the company also offers a more comprehensive security suite called AVG Internet Security 2011. This suite offers the same anti-malware protection as the free edition, but it also provides real-time protection against Internet search and social networking sites.

2: Comodo Antivirus

Comodo Antivirus takes a different approach to virus protection than most other antivirus products do. Comodo is based on the idea that it is foolish to allow code to run without first proving itself to be benign. So Comodo implements a default denial until an executable proves itself trustworthy. To keep the software from being too chatty, Comodo executes unknown code in an isolated sandbox where its behavior can be monitored without running the risk of the executable harming the system.

3: PC Tools AntiVirus Free 2011

PC Tools AntiVirus Free 2011 is a basic antivirus / anti-spyware program that is designed to protect Windows desktops against various forms of malware. Besides its basic detection capabilities, PC Tools includes a feature called Search Defender that is designed to warn you about unsafe Web sites (or phishing sites) before you click on them. The software also includes a File Guard component that monitors the file system and blocks attempted malware infections in real time.

4: Avast Free Antivirus

Like AVG, Avast sells comprehensive security suites, but makes its basic antivirus / anti-spyware product available for free to home users. Although I have never used Avast Free Antivirus, I’ve recently noticed posts in various message boards from people who claim that Avast provides better protection than some of the commercial products.

5: Ad-Aware Free Internet Security

Although it was originally designed as a product for detecting adware, Lavasoft’s Ad-Aware has evolved into a complete anti-malware product. Ad-Aware Free Internet Security provides real-time protection against spyware, rootkits, and more. It also includes a utility called The Neutralizer, which you can use to clean a PC that has already been infected.

6: HijackThis

HijackThis is one of my favorite anti-malware utilities, but it’s not for the faint of heart. HijackThis is designed to compile a report of critical file and registry settings that are often prone to viral infections. The thing that makes HijackThis difficult to use is that it makes no distinction between malicious and legitimate entries. As a result, you can end up doing even more damage to a PC unless you know what you are doing. Even so, I consider HijackThis to be a must-have utility.

7: Microsoft Security Essentials

Microsoft provides free antivirus protection for home users through a relatively new application called Microsoft Security Essentials. Microsoft Security Essentials is based on the same ForeFront technology as Microsoft’s enterprise class anti-malware software. The difference is that Microsoft Security Essentials is available solely to home users and businesses with fewer than 10 Windows desktops.

8: Windows Defender

Microsoft’s Windows Defender is a free anti-spyware utility for Windows. It’s not comprehensive, but it does a surprisingly good job of protecting Windows as long as you install it before an infection occurs.

Windows Defender is included with Windows Vista and Windows 7, but you can also download a version for Windows XP. If you are using Windows 7 or Windows Vista, Windows Defender is disabled by default. You can enable Windows Defender by typing the word Defender into the Windows search box and then double-clicking on the Windows Defender option. When you do, Windows will tell you that Windows Defender is turned off and will give you the opportunity to enable it.

9: Malicious Software Removal Tool

Although not a comprehensive antivirus tool by any stretch of the imagination, Microsoft’s Malicious Software Removal Tool does a good job of detecting and removing the most common viruses. The Malicious Software Removal Tool works with Windows 7, Vista, XP, and Server 2003. Microsoft releases updates to this tool on the second Tuesday of each month.

10: McAfee virus removal tools

McAfee makes commercial antivirus products, but it also offers some free tools for removing viruses. Specifically, it offers tools for removing Sasser, Bagle, Zafi, Mydoom, Lovsan / Balster, Klez, and Bugbear. You can download all of these tools here.