Block or Unblock usb drives

First of all

GO TO --> START --> RUN

Now type REGEDIT

Now look for the key :

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\USBSTOR

now find the key there called :-

"Start"
double click on it.
now change the value data 3 --> 4

where its base is Hexadecimal
here you go

U have done it
now close the registry and you'll see the result. yours PC's all usb ports are disabled

To Re-Enable/Unblock USB Ports just change the value data again 4 --> 3
now your PC's all USB Ports are Re-Enabled