Joe has a windows network without active directory. He needs to prevent one user from being able to write to a usb device – a little suspected espionage?? Here is your solution from howTogeek

Registry Hack to Disable Writing to USB Drives
A common
security concern at organizations is allowing users to plug in a usb flash
drive, because they could so easily copy corporate data.
Since Windows XP
SP2, you can disable writing to USB devices altogether using a simple registry
hack. Here it is:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\StorageDevicePolicies]”WriteProtect”=dword:00000001
You can also just download one of the following registry tweaks to enable or
disable writing to USB drives.

Enable USB
Write

Disable
USB Write

Once you use the registry hack, you will have to
reboot for the changes to take effect. One should also note that if you are
using this trick, you should make sure that the users are not administrators on
the computer, because they could easily change this setting back.
This works
on Windows Vista as well. Here’s the window you’ll get when you try and write to
a USB drive: