How can I mark my USB storage devices as read-only?

Windows XP Service Pack 2 (SP2) introduces a new registry subkey that lets you mark USB-based storage devices such as memory sticks as read-only devices. This is a useful security capability that can prevent users from copying data from their systems and taking that data offsite via a USB device. To enable the USB write protection, perform the following steps:

Start the registry editor (regedit.exe).
Navigate to the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlStorageDevicePolicies subkey. (Create the StorageDevicePolicies subkey if it doesn’t already exist.)
From the Edit menu, select New, DWORD Value.
Type the name WriteProtect and press Enter.
Double-click the new value and set it to 1. Click OK.
Close the registry editor.
Restart the computer.

To disable this change, you can either set WriteProtect to 0 or delete it.