The following registry setting will prevent writing to usb in windows xp.Expand HKEY_LOCAL_MACHINE\System\CurrentControlSet\Contro l Add 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.Giving a value of "0" will allow to write again
