Settings with Application scope are read-only. That's because they are stored in the main config file in the program folder, which users with limited accounts will not have write access to. Settings with User scope are read/write because a copy is stored under each user's Application Data folder. Every user is guaranteed to have write access to their own Application Data folder. Note though, that this means that if one user changes the setting values it will have no effect on any other users. This is a good thing in some situations and a bad thing in others. If I need to write to the main config file I implement my own class that does so through an XmlDocument object, but I always check that the current user has access to the folder first.