One of the main causes for virus infection is careless use of pen drives (USB sticks) and other removable medias. Because of the auto run feature of these devices, malware can easily get in to a computer by modifying the Autorun. Inf file. The most recent example is latest computer virus Conficker (aka Downup, Downadup and Kido) which is widely propagating through networks and USB drives. If infected, it disables many system services like computer Automatic Update, etc and is normally difficult to find out.

Because of the large amount of malware-related problems associated with Microsoft AutoRun, Panda security has created a free utility called Panda USB Vaccine for vaccinating USB drives and your computer.

USB Vaccination can be used on individual USB drives to disable its AutoRun.inf file in order to prevent malware infections from spreading automatically. It permanently blocks AutoRun.inf file and disables Windows from automatically executing any malicious file that might be stored in that particular USB drive.

The drive can otherwise be used normally, but they will be prevented from opening automatically. Panda USB Vaccine currently works on FAT & FAT32 USB drives only. Also remember that USB drives once vaccinated cannot be reversed.

You can also vaccinate your computer in order to disable AutoRun completely, so that no program from any USB/CD/DVD drive can auto-execute (You can also enable it at any time). This is a really helpful as there is no user friendly and easy way of completely disabling AutoRun on a Windows PC. [via- research.pandasecurity]