With the introduction of digital cameras, Apple's ipod, and high volume USB memory devices. The chances that an employee may carry protected data or copyrighted software out the door has become common. It is also possible that an employee may carry in stolen copyrighted software, or even a virus. Unlicensed software can result in extraordinary fines that can cripple a small business. If you are running a small or large business, it may be necessary to disable the USB ports on employee computers.
The following is the location within the system registry where Microsoft allows turning off or on the USB storage devices.

\SYSTEM\CurrentControlSet\Services\USBSTOR

The dword value for "Start" can turn on or off access to USB storage devices.
To disable USB access change the value to (4) to turn on external devices change it to (3)

I have included a simple program you may download to do it for you. USBADMIN.ZIP