Microsoft Security Essentials provides real-time protection for your home PC that guards against viruses, spyware, and other malicious software. It is a free download from Microsoft that is simple to install, easy to use, and always kept up to date so you can be assured your PC is protected by the latest technology. It’s easy to tell if your PC is secure — when you’re green, you’re good. It’s that simple.
Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.
Reviewing 4.6.0205.0 Pre-Release (Jul 8, 2014)
Very Good Antimalware, Light and effective
Reviewing 4.4.0304.0 (Nov 11, 2013)
May be good at guarding the PC,(while slowing it down), but not so good at removing infections, especially the rootkits involved. If you're going to slow your PC down with realtime security software, get something that can also remove what it is guarding against.
Reviewing 22.214.171.124 Pre-Release (Sep 10, 2013)
This would be great if I still used windows... I don't. Know windows, no security.
Reviewing 126.96.36.199 (Feb 27, 2013)
Have tried this I don't know how many times. Same result: VERY heavy on the PC with its background service running. Besides, realtime A/V software is really only for the internet clueless. I've learned to live without traditional system realtime A/V(spyware and malware) software protection and am doing just fine thank you, and the PC rewards me in return with the utmost speed.
BTW, this software keeps dragging down your system even when you turn off its realtime protection because of its constantly running background service.
Reviewing 4.139.1036.0 (Oct 31, 2012)
score very low in independent test
How do you download a version other than the one appropriate to the O/S you're currently running?
Answer: Click on the "Locales & Languages" link just below the big "Download Now" button at http://www.microsoft.com/security_essentials/
For United States (English), there are 3 versions available:
Windows XP 32-bit
Windows 7/Vista 32-bit
Windowns 7/Vista 64-bit
Download links to English XP 32-bit version.
To download versions for other OSs (Vista/7 32/64bit) or locales, use the "Homepage" link and click the big Download Now button in your face.