USB drives (also known as flash drive, mobile disk or pen drive) are becoming the most popular standard in these days to store and move data. USB support is available in PCs of both IBM-compatible and Apple computers. USB port support hot plugging and plug & play. The USB allows up to 127 devices to be connected to the bus via a single port. The driver name "usbstor.sys" is used to communicate any USB drives to the operating system.

USB drives are indeed very useful in these days but a user can easily use to transfer any confidential information from your computer to others and can also upload viruses affected files to your computer by accidentally or deliberately. But you can prevent the users to connect any USB drives in the computer by disabling the ability of "usbstor.sys" (USB driver) to load in system. It will block the USB storage devices only and your system USB keyboard, mouse and others USB devices will work properly.

Perform the following steps to block the USB storage devices:

First click on Start button to open "Run" and type "regedit" then press Ok button to open the Registry Editor.

In registry editor locate the given path:
Here select the "USBSTOR" folder and in right side of the registry editor panel find the value with name "Start".
Double click on "Start" and then set its value 4 under "Value data" section.
Close the Registry editor and restart your computer for changes to apply.

Now when you want to restore the default setting, open the Registry Editor and set its value back to 3.

Now again close the Registry editor and restart your computer for changes to apply.