This method retrieves the path to a system special folder, such as Program Files, Programs, System, or Startup, which can be used to access common information. Special folders are set by default by the system, or explicitly by the user, when installing a version of Windows.
The folder parameter designates the special folder to retrieve and must be one of the values in the Environment..::.SpecialFolder enumeration; any other value throws an exception.
For more information about special folders, see the CSIDL values topic.