ClamAV - Free & open sourceantivirus also the best.

ClamAV or WinClam

ClamAV or Clam Anti-Virus is an open source , free and community supported anti virus software.

It has many advantages and i personally recommend if for use in you P.Cs.

Now i will explain how you can use this amazing project from the international open source community.

DOWNLOAD:

Windows users: http://www.clamwin.com/

Other Users: http://www.clamav.net/download/

ubuntu users may activate the back port repository and install the latest version from the package manager.

USE:

Win clam has a GUI just like other antivirus systems.

The linux versions are are mainly command line based, but if you would like to have GUI, you may install CLamtk or KlamAV.

But i strongly recommend that you learn and use the command line , as it havs more advanced options.

Features:

• command-line scanner
• fast, multi-threaded daemon with support for on-access scanning
• milter interface for sendmail
• advanced database updater with support for scripted updates and digital signatures
• virus scanner C library
• on-access scanning (Linux® and FreeBSD®)
• virus database updated multiple times per day (see home page for total number of signatures)
  
• built-in support for various archive formats, including Zip, RAR, Tar, Gzip, Bzip2, OLE2, Cabinet, CHM, BinHex, SIS and others
  
• built-in support for almost all mail file formats
• built-in support for ELF executables and Portable Executable files compressed with UPX, FSG, Petite, NsPack, wwpack32, MEW, Upack and obfuscated with SUE, Y0da Cryptor and others
• built-in support for popular document formats including MS Office and MacOffice files, HTML, RTF and PDF

for more details or help 
feel free to contact me on 
http://blaisemcrowly.co.cc
blaise.crowly@gmail.com