a-squared - http://www.emsisoft..../software/free/
AntiVir - http://www.free-av.com/
Avast - http://www.avast.com...ast_4_home.html
AVG - http://free.grisoft.com/
BitDefender - http://www.bitdefender.com
ClamWin - http://www.clamwin.com/
Of those six (or any other anti-virus programs that are free) do you reccomend for the most thorough/effective scan?