This is the trick to remove some of the Virus which comes mostly from Pendrives, when you don't have a Antivirus installed or your Antivirus is not updated.Most of the Pendrive Viruses have an hidden "Autorun.inf" file inside them so that as soon as you double click on the drive icon the "Autorun.inf" file gets executed and the command in this file installs the Virus in your Computer.So, Mostly