What Is the Best Free Antivirus Software?

Ccleaner: PC cleaner and registry cleaner http://www.piriform.com/ccleaner

Ccleaner Enhancer: http://singularlabs.com/software/ccenhancer/
Eusing Registry cleaner: http://www.eusing.com/free_registry_cleaner/registry_cleaner.htm

Wise Registry & Disk Cleaner:  http://wisecleaner.com/wisediskcleanerfree.html
Glary Utilities: http://www.glarysoft.com/ 
IOBit Advanced System Care: http ://www.iobit.com/
IOBit All Tools: http://www.iobit.com/

Junk Files Optimizer: http://singularlabs.com/software/system-ninja/
Windows Essentials: http://www.microsoft.com/security_essentials/
Avast antivirus: http://www.avast.com/pr-avast-software
AVG AntiVirus: http://free.avg.com/us-en/homepage
Immunet AntiVirus: http://www.immunet.com/main/index3.html
Superantispyware: http://www.superantispyware.com/
Malwarebytes antimalware: http://www.malwarebytes.org/
Zone Alarm Free firewall: http://www.zonealarm.com/security/en-us/zonealarm-pc-security-free-firewall.htm
RevoUninstaller:http://revouninstaller.software.en.softonic.com/download?gclid=CIno5MuvnqYCFc9J2godEEB2oA
Auslogics disk defrag: http://www.auslogics.com/en/
Deflagler defrag: http://www.piriform.com/
EASEUS partition manager: http://www.partition-tool.com/

EASEUS Todo Backup: http://www.todo-backup.com/products/home/free-backup-software.htm
Calling ID (Browser) http://www.callingid.com/Default.aspx
Mailwasher: http ://www.mailwasher.net/
Skype: http://www.skype.com
Everything search engine: http://www.voidtools.com/

Open Office: http://www.openoffice.org/

PC Brother IE Care:  http://www.pc-brother.com/index.php/product/iecare

AllMyApps:  http://allmyapps.com/instant-setup

Easeus Todo Backup Home: http://www.todo-backup.com/download/

Paragon Backup & Recovery 2011 (Advanced) : http://www.paragon-software.com/home/br-free/download.html