string sPath = Environment.GetEnvironmentVariable("systemdrive");
Console.WriteLine(sPath);

//C:

// Sample for Environment class summary
using System;
using System.Collections;

class Sample 
{
    public static void Main() 
    {
    String str;
    String nl = Environment.NewLine;
//
    Console.WriteLine();
    Console.WriteLine("-- Environment members --");

//  Invoke this sample with an arbitrary set of command line arguments.
    Console.WriteLine("CommandLine: {0}", Environment.CommandLine);

    String[] arguments = Environment.GetCommandLineArgs();
    Console.WriteLine("GetCommandLineArgs: {0}", String.Join(", ", arguments));

//  <-- Keep this information secure! -->
    Console.WriteLine("CurrentDirectory: {0}", Environment.CurrentDirectory);

    Console.WriteLine("ExitCode: {0}", Environment.ExitCode);

    Console.WriteLine("HasShutdownStarted: {0}", Environment.HasShutdownStarted);

//  <-- Keep this information secure! -->
    Console.WriteLine("MachineName: {0}", Environment.MachineName);

    Console.WriteLine("NewLine: {0}  first line{0}  second line{0}  third line",
                          Environment.NewLine);

    Console.WriteLine("OSVersion: {0}", Environment.OSVersion.ToString());

    Console.WriteLine("StackTrace: '{0}'", Environment.StackTrace);

//  <-- Keep this information secure! -->
    Console.WriteLine("SystemDirectory: {0}", Environment.SystemDirectory);

    Console.WriteLine("TickCount: {0}", Environment.TickCount);

//  <-- Keep this information secure! -->
    Console.WriteLine("UserDomainName: {0}", Environment.UserDomainName);

    Console.WriteLine("UserInteractive: {0}", Environment.UserInteractive);

//  <-- Keep this information secure! -->
    Console.WriteLine("UserName: {0}", Environment.UserName);

    Console.WriteLine("Version: {0}", Environment.Version.ToString());

    Console.WriteLine("WorkingSet: {0}", Environment.WorkingSet);

//  No example for Exit(exitCode) because doing so would terminate this example.

//  <-- Keep this information secure! -->
    String query = "My system drive is %SystemDrive% and my system root is %SystemRoot%";
    str = Environment.ExpandEnvironmentVariables(query);
    Console.WriteLine("ExpandEnvironmentVariables: {0}  {1}", nl, str);

    Console.WriteLine("GetEnvironmentVariable: {0}  My temporary directory is {1}.", nl,
                           Environment.GetEnvironmentVariable("TEMP"));

    Console.WriteLine("GetEnvironmentVariables: ");
    IDictionary	environmentVariables = Environment.GetEnvironmentVariables();
    foreach (DictionaryEntry de in environmentVariables)
        {
        Console.WriteLine("  {0} = {1}", de.Key, de.Value);
        }

    Console.WriteLine("GetFolderPath: {0}", 
                 Environment.GetFolderPath(Environment.SpecialFolder.System));

    String[] drives = Environment.GetLogicalDrives();
    Console.WriteLine("GetLogicalDrives: {0}", String.Join(", ", drives));
    }
}
/*
This example produces results similar to the following:
(Any result that is lengthy or reveals information that should remain 
secure has been omitted and marked "!---OMITTED---!".)

C:\>env0 ARBITRARY TEXT

-- Environment members --
CommandLine: env0 ARBITRARY TEXT
GetCommandLineArgs: env0, ARBITRARY, TEXT
CurrentDirectory: C:\Documents and Settings\!---OMITTED---!
ExitCode: 0
HasShutdownStarted: False
MachineName: !---OMITTED---!
NewLine:
  first line
  second line
  third line
OSVersion: Microsoft Windows NT 5.1.2600.0
StackTrace: '   at System.Environment.GetStackTrace(Exception e)
   at System.Environment.GetStackTrace(Exception e)
   at System.Environment.get_StackTrace()
   at Sample.Main()'
SystemDirectory: C:\WINNT\System32
TickCount: 17995355
UserDomainName: !---OMITTED---!
UserInteractive: True
UserName: !---OMITTED---!
Version: !---OMITTED---!
WorkingSet: 5038080
ExpandEnvironmentVariables:
  My system drive is C: and my system root is C:\WINNT
GetEnvironmentVariable:
  My temporary directory is C:\DOCUME~1\!---OMITTED---!\LOCALS~1\Temp.
GetEnvironmentVariables: 
  !---OMITTED---!
GetFolderPath: C:\WINNT\System32
GetLogicalDrives: A:\, C:\, D:\

*/