Microsoft Security Essentials

 
That is the Best Application {Software} of the give microsoft ,so its 100% free for genuine windows operating systems that is simple to install, easy the use, and always keep up-to-date so you can be assured your PC is protected by the latest technology,
Supported operating systems: Windows 7, Windows Vista, Windows XP,Your PC must run genuine Windows to install Microsoft Security Essentials. Learn more about genuine
                                    "Before installing Microsoft Security Essentials, we recommend that you uninstall other antivirus software already running on your Pc" Running Some  antivirus program at the same time can potentially cause conflicts that affect PC performance.

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Minimum system requirements for Microsoft Security Essentials

* Operating System: Windows XP Service Pack 3 (SP3) Windows Vista (Service Pack 1, or Service Pack 2)  Windows 7
 * For Windows XP, a PC with a CPU clock speed of 500 MHz or higher, and 256 MB RAM or higher.
 * For Windows Vista and Windows 7, a PC with a CPU clock speed of 1.0 GHz or higher, and 1 GB RAM or higher
  * VGA display of 800 × 600 or higher.
 *  200 mb hdd space
 *   An Internet connection is required for installation and to download the latest virus and spyware definitions for Microsoft Security Essentials.