Autoplay must be disabled for all drives.

Allowing autoplay to execute may introduce malicious code to a system. Autoplay begins reading from a drive as soon as you insert media in the drive. As a result, the setup file of programs or music on audio media may start. By default, autoplay is disabled on removable drives, such as the floppy disk drive (but not the CD-ROM drive) and on network drives. If you enable this policy, you can also disable autoplay on all drives.