I use the bit defender boot disc and the Kapersky boot disc to get rid of any nasties as they boot into linux and bypass the HDD boot altogether, makes it far easier to remove root kits and persistent viruses. They both will autoupdate on booting to the latest virus definitions. Well worth having on the shelf.
They have a text only mode or GUI mode and are very easy to use.
http://rescuedisk.kaspersky-labs.com...isk/updatable/
http://download.bitdefender.com/rescue_cd/