Disable USB ports to block external drives and sticks, with Windows USB Blocker
Windows USB Blocker is a free and efficient utility that lets you control your USB ports to block storage devices, drives and sticks, without causing any problem to USB connections used by non storage devices like speakers, keyboards or mice.
Note that when USB ports are blocked, even if you connect a drive its letter won’t appear in Windows Explorer.
The program is (and couldn’t but be) simple as you can guess; you won’t face any difficulty using it. A click is enough to activate or deactivate the connection to USB drives.