Autorun is a common worm that spreads on removable drives, that is rather difficult to remove.
Variants of Autorun are worms that spread by copying themselves into the root directories of hard drives and other writable media such as USB memory sticks. It deletes important and useful programs, locks the Task Manager, and obtains administrator rights. It then fills up all remaining space with copies of itself.
This worm and variants create an autorun.inf file in root directories of drives.