How do I locate the application servers available in the
registry of the machine?

Read the registry key under HKEY_CLASSES_ROOT\CLSID\* looking
for keys that have a subkey "Borland DataBroker".  These
entries are application servers.  Here's an example that
loads application server names to a Listbox.

procedure TForm1.FormCreate(Sender: TObject);
var

uses Registry;
  I: integer;
  TempList: TStringList;
begin
  TempList := TStringList.Create;
  try
    with TRegistry.Create do
    try
      RootKey := HKEY_CLASSES_ROOT;
      if OpenKey('CLSID', False) then
        GetKeyNames(TempList);
      CloseKey;
      for I := 1 to TempList.Count - 1 do
        if KeyExists('CLSID\' + TempList[I]
          + '\Borland DataBroker') then
        begin
          if OpenKey('CLSID\' + TempList[I] + '\ProgID', False)
            then begin
              Listbox1.Items.Add(ReadString(''));
              CloseKey;
            end;
        end;
    finally
      Free;
    end;
  finally
    TempList.Free;
  end;
end;