If the USB storage device is already installed in system:
1. Type regedit in RUN dialog box and press Enter. Now go to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UsbStor
2. In right-side pane, change value of "Start" to 4
3. Now whenever a user will attach a USB storage device which is already installed in system, Windows will not detect it and it'll not be shown in My Computer.
NOTE: If you want to revert it back to default, then change the value of "Start" to 3
BONUS TIP: If you want to restrict only writing to USB storage devices, then take a look at Point 21 in following tutorial:
1. Type regedit in RUN dialog box and press Enter. Now go to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UsbStor
2. In right-side pane, change value of "Start" to 4
3. Now whenever a user will attach a USB storage device which is already installed in system, Windows will not detect it and it'll not be shown in My Computer.
NOTE: If you want to revert it back to default, then change the value of "Start" to 3
BONUS TIP: If you want to restrict only writing to USB storage devices, then take a look at Point 21 in following tutorial: