I tried it on a fast machine (2.6 GHz Dual-Core) and it ate up the CPU. I would imagine putting it on an older machine would effectively render the machine un-usable.

Sorry, post unrelated to who I am answering to, but I think this is seriously important.

Way to mess it up Lee. Mess it up REALLY bad, enough to misinform all your readers that don't have a keen enough eye.
MSE doesn't get the "best free antivirus for Windows" title. Not even Ars claims that. Know why?

THIS IS A FREAKING MALWARE REMOVAL TEST LEE!!!

It's about malware removal. We're talking adware and the likes here, not viruses. What AV-Comparatives tested was in fact the anti-malware portion of every software on their list, not their antivirus portion. MSE might get an Advanced+ note in this round, it doesn't mean it will get such a note in virus detection. Or even malware detection, as they have picked very specific test files without disclaiming their full name. They were just testing the removal of some, remember?
The way you wrote it you are implying that MSE was crowned king of free antivirus by AV-Comparatives. This is terribly erroneous and far from truth. Everyone reading your article is led to believe MSE is the best thing since sliced bread and while it is great, it's not that. :/

I'm sorry for the cold, expressive reply, but it's horrible to misinform people whether that was the point or not.

I absolutely agree with your definition of malware, virus are only one of the few bad software attacking your computer.

However, your title and half of your article clearly states that AV-Comparatives has rated MSE the best free antivirus for Windows.
This is not the case whether you use your definition of malware or the more widely accepted definition referring to "adware", the later definition being used by AV-Comparatives themselves. If you look at the test samples you will see none of those are actual virus as they are not meant to harm the computer (that's left open to discussion... but you get the gist of it.)

If MSE was the best rated free something, it would be the best rated free anti-malware/adware. Not antivirus, as once again those tests show absolutely NO virus samples. Would you say a certain computer was the best computer if it was K6-2 era but it had the biggest, most efficient power supply you've ever seen? It's a silly example, but it's exactly what this article is leading readers to believe.

Calling MSE the best rated free anti-malware/adware would be erroneous too. Those tests show only removal of a few select samples. Not detection or pro-active protection. Ars was careful in not over hyping MSE, referring to the products as security products and only presenting the facts, you have twisted them. :S

Frankly the article appears to me as a lot of sensationalism (whether or not that was wanted) and it conveys false information in doing so. That's a double no-no. It's nothing I have seen previously from your articles which really makes me wonder if you haven't suddenly turned in a fanboy or it's a honest mistake.

Doesn't really matter much anymore, MSE is the best now

Erm you have to be kidding right? Comodo may have one of the best firewalls around, but their AV tech still leaves MUCH to be desired, its a long way from being competitive with the ones in this test.

Comodo isn't in the same league yet. Check this post:
http://www.downloadsquad.com/2009/10/24/six-free-antivirus-programs-made-for-your-windows-7-system/

Comodo had a 74% detection rate - I wouldn't touch any antivirus that misses 1 in 4 malware objects.

The test is based on SSTS:

Security Software Testing Suite (SSTS) is a set of tools used for testing Windows security software that implement application-based security – i.e. most of the Internet security suites, HIPS, personal firewalls, behavior blockers etc. SSTS is based on the idea of independent programs that attempt to bypass various features of the security software.

Good score in this test doesn't mean that the product is good at detecting and removal of viruses and malwares.

Matousec is testing firewalls not AV

Nope that test is for firewalls and yes Comodo is best for that, but has nothing to do with AV detection.

The test is about firewalls, NOT AV programs.

Hey "guy/gal " do yourself and "your computer" a favor...uninstall Comodo everything and then go over here to www.scanwith.com look for "Avast beta 5"..yes it's still being tested but it's way ahead of '' any product" by Comodo.

A benefit of which is you get too use the latest flavor for free while it's in beta, oh and it took about 5 version releases before I would even use their beta myself ( It's ready now ....oh is it ever) Now let's see if it stays free like Avast said "Home Version" would.

Wait till you try to get rid of that wacky "firewall" you'll have to download a CMD (comand line file) and execute it to clean your machine of it "which is bad software code creating. I know this because I used too trust Comodo also back in the day. Till I found out all the "crap you had to go through" to get rid of just their firewall. Windows firewall is Ok and all you really need XP SP 3 Vista's is better and Windows 7 is even better most don't like the fact that there is no "out bound " control but this can be configured with "rules" under advanced. I'm not going to tell you you have to use something else it's your computer "your putting yourself at risk." I don't know where you surf...and really don't care.

But don't get in a "mine is bigger" match with these "cats" it's not a crime to not know the only crime is once you find out....not being willing to address the issue(s). I wish you happy computing anyway. I usually wouldn't take the time to write a comment to someone...but if I can save one computer from having to be "recovered after a malware attack" . (Or restored from DVD)

I've done my "deed" for the day. Now you do what you will "Guy/Gal " but don't say no one "warned you". May you enjoy your day. And remember "we're not here to pick on anyone" we all are just trying to keep everyone who reads this blog informed.

If it was part of the OS then Microsoft would just face more antitrust lawsuits from whiny morons. Also, it would only not be needed if people didn't write viruses attacking the most common OS in the world. You can't cause mass chaos by targeting Mac & Linux system when they have so little market share for the mainstream user.

Bad luck? MSE has been very light on resources on all the machines *I've* installed it on, so I have no idea what the issue you had was. Hope you have better luck in the future.