Prevent users from using USB removable disks (USB flash drives)

Whenever a new USB device is plugged-in to a USB port, the operating system checks
the device and hardware id to determine if it's a storage device or not. If it determines that
it is indeed a mass storage device it will load the appropriate driver, and will display the
device as a drive in the Windows Explorer tree view. This is done by using the
usbstor.sys driver.
If the device does not have a drive letter, you will need to assign one to it by using the
Disk Management snap-in found in the Computer Management tool.
If you disable the ability of the usbstor.sys driver to run on the computer, you will in fact
block the computer's means of discovering the flash drive and loading the appropriate
driver.
Note: This tip will allow you to block usage of USB removable disks, but will continue
to allow usage of USB mice, keyboards or any other USB-based device that is NOT a
portable disk.
Block usage of USB Removable Disks
To block your computer's ability to use USB Removable Disks follow these steps:
1. Open Registry Editor.
2. In Registry Editor, navigate to the following registry key:
3. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\USBSTOR
4. Locate the following value (DWORD):
Start
and give it a value of 4.
5. Close Registry Editor. You do not need to reboot the computer for changes to
apply.
Enable usage of USB Removable Disks
To return to the default configuration and enable your computer's ability to use USB
Removable Disks follow these steps:
1. Go to the registry path found above.
2. Locate the following value:
Start
and give it a value of 3.