USB drives are extremely handy tools, but in some instances it might not be a good idea to allow users to write onto these devices from their PCs. This is especially true when working with highly confidential data or intellectual property at work. Users of Windows XP with service pack 2 installed can disable writing to USB devices.
To do this:
Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
From there right click and create a new key and name it "StorageDevicePolicies". In the window on the right then create a new DWORD value and label it WriteProtect, give it a value of "1" and users can no longer write to USB drives. To re-enable this option change the value to 0 and users are again allowed to write.
The modifications you made will be in effect after you reboot your PC.