uses Registry; 

procedure TForm1.GetDataSourceNames(System: Boolean); 
var 
  reg: TRegistry; 
begin 
  ListBox1.Items.Clear; 

  reg := TRegistry.Create; 
  try 
    if System then 
      reg.RootKey := HKEY_LOCAL_MACHINE 
    else 
      reg.RootKey := HKEY_CURRENT_USER; 

    if reg.OpenKey('\Software\ODBC\ODBC.INI\ODBC Data Sources', False) then 
    begin 
      reg.GetValueNames(ListBox1.Items); 
    end; 

  finally 
    reg.CloseKey; 
    FreeAndNil(reg); 
  end; 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
begin 
  //Системные DSNs 
  GetDataSourceNames(True); 
  //Пользовательские DSNs 
  GetDataSourceNames(False); 
end;