I am with cracked McAfee for 3 years and I am very satisfied. I do not understand why you ask for "free" version? I use cracked antivirus, cracked win7, cracked office 2007, cracked photoshop, cracked dreamweaver, cracked CCleaner, cracked IM tools. BUT if you want the best FREE Antivirus then this is "Format C". I have doubled my hard disk, half is windows and programs, another are all my files. And remember no one virus will damage your computer until you give him access, therefor if you install some program and do not sure then use virtualbox or something similar.
Hope this helps,
Regards,
Estek