What is the best free anti virus program?

I use these programs to clean friends computers.

It helps speed up the system and usually

works every time unless there is some very unusual virus on the system.

They are all free programs.

1)Get spybot search and destroy, install, update and run.

http://www.safer-networking.org/en/index...

2)Get avgfree anti virus, install, update and run.

http://free.grisoft.com

3)Get windows defender antispyware, install, update and run.

http://www.microsoft.com/downloads/detai...

4)Get avgantispyware, install, update, and run.

http://free.grisoft.com/doc/download-fre...

5)Get Avira antivirus, install update, and run(dont use both AVG and Avira, pick one)

http://www.avira.com/en/pages/index.php

What is the best free anti virus program?microsoft office

bitdefender iys pretty sweet.

What is the best free anti virus program?norton antivirus

Avast, AVG