I hear from those who have tried it that it is SUPER!  Microsoft Security Essentials will be available for Windows XP SP2 or SP3, Windows Vista and Windows 7 including Windows XP mode on both x32 and x64 PCs.

More info HERE:

This is exciting news. But when I click on the links, I get the following:

"Not available in your country or region
You appear to be in a country or region where the Microsoft Security Essentials Beta is unavailable.

This beta is available only to customers in the United States, Israel (English only), People's Republic of China (Simplified Chinese only) and Brazil (Brazilian Portuguese only)."

Hopefully this will change tomorrow. When I last trialed MSE, I was very impressed.

The "official" (non-Beta) is now available, for those interested:

http://www.microsoft.com/Security_essentials/

From Sunbelt: Thoughts on MSE

Well, this small file downloaded with no problem and then proceeded to do a lengthy update, after one false start...something about not liking my connection. I was advised to turn off my AV and other spyware products. but didn't then because it wasn't loaded and installed at that point. The interface is simple and appears easy to use. This installation is on my Vista XPS and I will let it run for awhile with AntiVir active. From what I gather about this product ,is that it is a fully functional AV and I should be able to safely deactive my Avira AV. It's now bedtime and will check this out more tomorrow and see if any conflicts pop up.

Also note:

- You must uninstall your current AV (not just disable its real-time shield) prior to installing MSE.
- In WinXP, installing MSE will remove Windows Defender
- As far as I can tell, there is no provision to install or use MSE as an on-demand scanner only.

I will let it run for awhile with AntiVir active. From what I gather about this product ,is that it is a fully functional AV and I should be able to safely deactive my Avira AV.

Thanks for the warnings, but being a researcher I have the curiosity to try things if I am pretty sure I won't get into unrecoverable trouble. So here are my observations about MSE:

Win Patrol alerted to a Start Menu change, Online Armor did not notice anything.

Windows Defender has been turned off.

All security products including MSE updated normally.

AntiVir did not detect MSE or vice versa during scans.

Quick scans by MBAM, SAS,  and A-Squared Free did not detect anything and MSE did not detect them.

I will go ahead and uninstall AntiVir. I am not sure how to set the various alert levels so will see what you all suggest. Apparently there is no opt-out of the Spynet feature, we get a choice between basic and advanced. This product is easy to use and I will be anxious to hear of others experiences. I plan to install MSE on my XP computer in a few days and perform the same tests.

I am not too concerned about automatic or scheduled updates or extra features. I do have it set up so that I am only notified of Windows updates and I let Avast update automatically, since that usually happens shortly after I sign on. All other products are updated manually daily and scans are run at reasonable intervals. MSE seems to be simplicity itself and easy to use. I am curious to see how thoroughly and accurately it gets the job done, so I will very interested in the test results that will surely come later. But perhaps I might just leave it on the computer it's on, as this XP has 1 Gig of memory and it's apparently still unclear if that is a requirment or not.

I'm going to hold off on trying MSE for now, because of all the hassles of uninstalling/ reinstalling my paid AV and WD, re-educating my firewall, re-configuring WD etc. and the potential for conflict with on-demand scanners or my HIPS protection.

I also have potential concerns over the EULA:
http://www.microsoft.com/security_essentials/eula.aspx#mainNav
(WGA-Notification by other means? The EULA is vague as to what "other Microsoft programs" might be installed without express permission of the user).

To my mind, the advantages of MSE over 3rd party free AVs and antimalware are:

1) Simplicity (installation, configuration, and use)
2) Guaranteed compatability of AV&AM
3) The huge malware database MS has to draw on
4) No nags or upgrade ads.

In short, it seems to be a "fire and forget" security solution for those not interested in having to deal with security programs, who wish only free, simple protection, without the bells and whistles.

But for those currently using (and happy with) avast or Avira Free, the MSE AV protection remains untested and unproven against the formers' track records. And when all is said and done, it remains a barebones security suite, with all the limitations of a suite. I too will be interested to see how the independent test sites find MSE at blocking, detection and removal.

For those like Dale who choose to try it- keep us updated on how you find it!

Note: Matt at remove-malware.com gives his recommended MSE settings:
http://remove-malware.com/antimalware/my-tools/moving-to-mse-%e2%80%93-my-microsoft-security-essentials-settings/

Just a side-note for anyone who's considering "looking" for [or testing] another free anti-virus program... that Avast is expected to release a completely revised version 5.0 sometime this month (October).

http://blog.avast.com/2009/07/20/avast-5-is-coming-soon/#more-354

Hi RD:

I saw the same report in the Washington Post online, as well as the Register.UK

None of these reports give links to the original AV-Test report which has been claimed to be "published", and it is not to be found on AV-Test.org 's website. While I have no reason to disbelieve the summary results reported 2nd hand by publications, I would place more trust in the full original test report. AV-Test has a history of being commissioned by vendors and magazines to perform non-comparative tests on single products, and ethical testers would disclose this in the full report.

Still, some promising early test results, (with a few reservations).

Edit for correction. 

Re:  the release of avast 5, looks like it's being delayed a bit longer:

"Second half of November according to the current schedule.
With a possible soft launch of the free AV (via a partner) a few weeks before that."

(Whatever that second sentence may mean/imply)

http://forum.avast.com/index.php?topic=49146.0

(No link to the test here, either.)

"Microsoft's Free AV Looks Good in New Test Results"

http://pcworld.co.nz/pcworld/pcw.nsf/feature/1545F1D0B613C0C6CC257645006EC471

http://www.pcmag.com/article2/0,2817,2353447,00.asp

For what it's worth until there is more testing.