Microsoft Security Essentials is one of the most popular anti-malware programs. It can be installed for free on a licensed copy of Windows XP, Vista, or Windows 7. In Windows 8, Security Essentials is replaced by Windows Defender. For previous versions, Windows Defender works only as anti-spyware.
Security Essentials is better than other anti-viruses in many ways. First of all, it uses of computer memory and CPU power. It also has an accurate scanner that results in the least number of false positives. Hence, it is most suitable for people who download many executable files from the Internet.
Unlike other security tools, this application sits quietly in the system tray, without any popup messages, unless a serious virus is detected. Often, scan for malware takes place without notifying the user. Default actions such as ‘Delete’ or ‘Quarantine’ are taken depending upon the severity of the infection. Daily updates from Microsoft ensure that your computer would be protected against new threats.
Advanced users can benefit from the settings page. Here, you can specify the locations to exclude from scanning. You can also join the MAPS (Microsoft Active Protection Service), which automatically collects information about the infections on your computer to make improvements in the program.
What I like most about the Security Essentials service is the "Submit a sample" page on their website. Here, you can upload any file that you suspect to be of danger to your PC. The developers would analyze it and add to the virus detection database so that others, including you, are protected from it. I have been using Security Essentials for many years, and haven't had any problems with viruses.