You may want to block USB mass storage device to disallow the unauthorized use of pendrives or you may want to unblock USB mass storage device to get access (most of the case in college’s net lab). Well, this can be done by a simple registry tweak. Before doing so, I recommend taking a backup of the regustry because playing with registry can be harmful for your OS The advantage of this is, you restrict users from copying and transferring sensitive data to and from the computer. This is mostly a necessity in: offices to protect intellectual property and cybercafe / public browsing centers to prevent users from knowingly or unknowingly infecting the system with viruses. Here’s how you can disable USB storage device drive access in windows :

1> Click on "Start –> Run –> Type regedit and hit Enter.”

 2> Navigate to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UsbStor”

3> Select the key UsbStor and double click on the Start value, which can be found in the right pane.

 4> In Value data part, put 4 (numeric value four), if you want to disable USB storage and put in 3 (numeric value 3), if you want to enable USB storage on your computer. 

The change will be effective immediately, however sometimes a reboot may be required. This hack will ensure that all the USB storage devices are disabled / blocked or enabled according to your choice.