In certain environments, it can be useful to disable the Windows USB storage driver to prevent end-users from using USB devices to copy data from the system.
You can do this easily by modifying the Windows registry.
Click Start, and run regedit
Navigate to HKEY_LOCAL_MACHINESystemCurrentControlSetServicesUSBStor
and set the Start value to 4.
The default of 3 is shown in the screenshot below.