C# properties.settings file

Application Settings (represented by Properties.Settings in C#) are in fact stored in configuration files and so are intimately connected with them.  Check this link for an overview:

http://msdn.microsoft.com/en-us/library/k4s6c3a0.aspx

I'd draw your attention in particular to these two paragraphs:

"Application settings works by persisting data as XML to different configuration (.config) files, corresponding to whether the setting is application-scoped or user-scoped. In most cases, the application-scoped settings are read-only; because they are program information, you will typically not need to overwrite them. By contrast, user-scoped settings can be read and written safely at run time, even if your application runs under partial trust. For more information about partial trust, see Security in Windows Forms Overview.

Settings are stored as XML fragments in configuration files. Application-scoped settings are represented by the element, and generally are placed in app.exe.config, where app is the name of your main executable file. User-scoped settings are represented by the element and are placed in user.config, where user is the user name of the person currently running the application. You must deploy the app.exe.config file with your application; the settings architecture will create the user.config files on demand the first time the application saves settings for that user. You can also define a block within app.exe.config to provide default values for user-scoped settings."

This link about managing application settings is also worth reading:

http://msdn.microsoft.com/en-us/library/a65txexh.aspx