Prevent Writing to USB Storage Devices

It is too easy for users to connect a device (USB-key or MP3 player) to the USB port of a computer, and copy things off the system. This is an obvious security risk. This has been addressed in Service Pack 2 for Windows XP. You have to manually add the following registry key:
Start the Registry Editor(Start-->Run-->regedit)
Go to the HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control key
If there is no key called StorageDevicePolicies, create it. You do this by right-clicking the HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control key, and selecting New > Key from the menu.
Select the StorageDevicePolicies key
From the menu select Edit > New > DWORD Value
Name the new value WriteProtect
Right-click the WriteProtect value and choose Modify
In the Value Data: box enter 1
Exit the registry editor, and restart your computer
To reverse, just delete the new WriteProtect value (or set the value to 0) and restart the computer.
Note: works on Windows XP Service Pack 2 only!