Windows System Folders

// Sample for the Environment.GetFolderPath method
using System;
class Sample
{
    public static void Main()
    {
    Console.WriteLine();
    Console.WriteLine("GetFolderPath: {0}",
                 Environment.GetFolderPath(Environment.SpecialFolder.System));
    }
}
/*
This example produces the following results:
GetFolderPath: C:\WINNT\System32
*/

Environment.SpecialFolder Enumeration
http://msdn.microsoft.com/en-us/library/system.environment.specialfolder.aspx