How to get Environment Vars 

//
// ENVIR. This sample shows how to get process environment strings and
// values of individual environment variables. Uses GetEnvironmentStrings
// and GetEnvironmentVariable functions from WIN32 API
//
unit EnvUnit;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    Edit2: TEdit;
    ComboBox1: TComboBox;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
var
 DosEnv  : PChar;
 I       : Integer;
 SignPos : Integer;
begin
//
// GetEnvironmentStrings = 32-bit version of GetDosEnvironment
//
 Memo1.Lines.Clear;
// Get all environment variables
 DosEnv := GetEnvironmentStrings;
 While DosEnv^ <> #0 do
  begin
// Add one by one into memo
   Memo1.Lines.Add(StrPas(DosEnv));
// Get next one
   Inc(DosEnv, StrLen(DosEnv)+1);
  end;
// Fill in ComboBox
  With Memo1 do
  begin
   for I := 0 to Lines.Count-1 do
    begin
     SignPos := Pos('=',Lines[I]);
     ComboBox1.Items.Add(Copy(Lines[I], 1, SignPos-1));
    end;
  end;
// Show 1st element
  ComboBox1.ItemIndex := 0;
  ComboBox1.OnChange(Self);
end;
procedure TForm1.Button2Click(Sender: TObject);
var
 Name, Value : PChar;
begin
// Get memory
   Name := StrAlloc(255); Value:= StrAlloc(255);
// Convert to PChar
   StrPCopy(Name, ComboBox1.Items[ComboBox1.ItemIndex]);
// Get variable value
   GetEnvironmentVariable(Name, Value, 255);
// Show it as Pascal string
   Edit2.Text := StrPas(Value);
// Free memory
   StrDispose(Name); StrDispose(Value);
end;
end.