Do your PC’s or network contain important confidential data, and are you afraid of data theft by employees?

In that case take a look at this article, it describes how to disable USB mass storage devices (USB pens, disks) on machines complete with GPO/ADM templates and all.

http://diaryproducts.net/about/operating_systems/windows/disable_usb_sticks

Based in part on this article (German);
http://www.gruppenrichtlinien.de/index.html?/HowTo/usb_sticks_deaktivieren.htm