Microsoft Security Essentials PC Software Free Download

It is a free product you can download to help defend computers running Windows XP, Windows Vista, and Windows 7 against viruses, spyware, and other malicious software. 

• Comprehensive protection—Microsoft Security Essentials helps defend your computer against viruses, worms, Trojans, and other malicious software and provides you with free spyware protection.
• Easy to get, easy to use—Microsoft Security Essentials is available at no cost, so there's no registration process that requires billing or personal information collection. It installs after a quick download and Genuine Windows validation and then stays automatically up to date with the latest spyware protection technology and signature updates.
• Quiet protection—Microsoft Security Essentials doesn't get in your way. It runs quietly in the background and schedules a scan when your computer is most likely idle. You only see alerts when you need to take action.

After click on download button you'll get this:

 Please follow the above mentioned instructions.