Dear PropellerHeads: A recent incident has led me to believe that I should have anti-virus software. Can you recommend one that is good and cheap?

A: Wow, an "incident," huh? Sounds scary, or at least like an episode from "Lost." Let's hope your budget and my answer will allow an outcome better than that show had.

As far as cheap goes, is free cheap enough for you? There are a slew of free anti-virus and anti-malware options available to you. Here are some of the more popular ones: avast! Free Antivirus (www.avast.com), AVG Anti-Virus Free (free.avg.com), Avira Anti-Vir Personal (www.avira.com/free), ClamWin Free Antivirus (www.clamwin.com), Comodo Antivirus (antivirus.comodo.com), Microsoft Security Essentials (www.microsoft.com/security_essentials) and finally PC Tools Antivirus (www.pctools.com/free-antivirus).

All of these will offer active protection for your system and permit on-demand and scheduled scans of your system files, though some schedulers are definitely better than others in terms of flexibility. Also, all will keep themselves up-to-date with the latest virus definitions for emerging threats. However, again, not all will allow you to decide how often or even when those updates may occur.

These products tend to divide themselves into three classes based upon a mixture of things, but predominately focusing on the number of features and the quality of the user experience. The high-end includes avast! and AVG, the mid-level includes ClamWin and PC Tools, while the low-end has Avira, Comodo and Microsoft.

Though I divide these into classes, I should emphasize that a high end solution may not be the best for everybody. Power users or those users who are willing to sacrifice some level of protection in exchange for minimal impact upon their everyday computing activities may very well opt for a low-end solution.

The key to configuring avast! and AVG properly is during the all-important setup process. Both of these products will want to install a slew of extra gadgets and options, pretty much all you don't need. AVG in particular was annoying about this. But avast! wants you to register, which I find even more annoying.

Once installed, both behave about the same with avast! taking up a little less memory than AVG, but both performing about the same. It is really a toss-up here on which one is better. Both offer active email and Web browsing scanning. This is evident in search results, where a green OKcheckmark will appear next to sites that are reported to be malware-free.

In the mid-level class, the amount of crap the setup programs want to install gets trimmed down to just a toolbar. Skip it. But in this class the differences between the products get a bit more pronounced.

ClamWin's user interface is straight out of 1998, which does not encourage much confidence. And although it takes up the least amount of disk space and active memory, it seemed to have the greatest negative impact on system performance.

Contrast this with PC Tools, which takes up a lot of disk space and memory, but also picked up a lot of tracking browser cookies. Though these don't contain viruses, I did appreciate their looking out for my privacy and for this reason I would recommend PC Tools Antivirus the mid-level class.

And finally, in the low-end, I'm going to throw Comodo right out. In addition to taking up the most disk space and asking that I change my DNS servers (really?), its user interface is as understandable as Chinese stereo instructions.

My recommendation would be Avirahere, not because it is really any better, but for the sole reason that Microsoft Security Essentials sucks up two to three times the memory as any other product. More than Outlook! Why, Microsoft, why?

So there you have it. Hopefully one of these guys will prevent another incident from occurring on your computer while also preventing an incident in your pocket book.

When the PropellerHeads at Data Directions aren't busy with their IT projects, they love to answer questions on business or consumer technology. Email them to questions@askthepropellerheads.com or contact us at Data Directions Inc., 8510 Bell Creek Road, Mechanicsville, VA 23116. Visit our website at www.askthepropellerheads.com.