I have tried just about all of these and, while none of them are out right dangerous, I can't really recommend them to anyone but light users or individuals who don't use the web much. I think that any organization with sensitive data would be best served going with a reputable antivirus company. You just cannot take risks with security, and in my opinion many of these free options are risky ones.

iObit Security 360 free edition
http://iobit.com/security360.html?Str=download

ClamWin (Portable)
http://portableapps.com/apps/utilities/clamwin_...

ThreatFire: http://www.threatfire.com
MalwareBytes: http://www.malwarebytes.org/

ThreatFire is a free anti-malware / anti-virus program that works with Windows. It's made by PC Tools, and there is a paid version available (called ThreatFire Pro). From what I've seen, ThreatFire works well. It's also quite light on system resources too, which is a good thing.

MalwareBytes is another good one, though I use it more for scanning a file than scanning my machine. I find that it's more thorough when a file is being scanned - it's found infections no other program has for me. Like ThreatFire, it's free, though there is a paid version available.

PC Tools Free Antivirus:
http://www.pctools.com/free-antivirus/

A-Squared Free:
http://www.emsisoft.com/en/software/free/

i just saw your video that you needed help finding more software.

Microsoft Security Essntials - http://www.microsoft.com/Security_Essentials/

theres this guy on youtube that does security software reviews and tests

http://www.youtube.com/mrizos

go there to find other ones.

Microsoft Security Essentials
A-Squared Free

Panda Cloud:
http://www.cloudantivirus.com/en/