Hello,
You can view free vs. paid comparison here:
http://free.avg.com/ww-en/download-avg-anti-virus-free
You can download AVG Free here:
http://free.avg.com/ww-en/download-free-antivirus
Installer will detect the operating system you are using and will download needed installation files.
Thanks
Which version is best for windows 7 64 bit?

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