According to S!Ri (Merci pour la sample):
Security essentials 2011 is a fake security software (rogue). It replaces Security essentials 2010, Internet Security 2010 and Advanced Virus Remover.
Security essentials 2011 displays a lot of warning messages, change the desktop background, detects fake infections and blocks softwares execution. It comes from fake online scanners, malicious porn sites, fake cracks and exploits.
If you need to clean your computer and Security essentials 2011 is blocking legit cleaners execution, enter any email and use this serial to register: ISR10F7D9MP3B2A
If your PC is infected with Security essentials 2011, use MBAM to remove the infection.