IF U DONT WANT ANYBODY TO INSERT PENDRIVE TO UR SYSTEM–HERE IS THE TRICK
go to START> RUN > and type REGEDIT to open the registry editor.
in the left pane, navigate to COMPUTER\HKEY_LOCAL_MACHI NE\SYSTEM\CURRENT-CONTROLLSET\SERVICES\USBS TOR double click on the entry named START in the right pane
change the value data: field to 4. press ok to save it.
if you want to revert back to the default configuration and enable your computers ability to use usb drives, just set the value of START to 3 again.