Code:
function EnumFontClBack(var lp: TEnumLogFont; 
  var tm: TNewTextMetric; 
  dwType: DWORD; 
  lpData: lParam): Integer; stdcall; 
begin 
  Result := 1; 
  with TForm1(lpData), Combobox1 do 
  begin 
    Items.Add(lp.elfLogFont.lfFaceName); 
  end; 
end; 


procedure TForm1.FormShow(Sender: TObject); 
begin 
  EnumFontFamilies(Canvas.Handle, nil, @EnumFontClBack, Integer(Self)); 
end; 

procedure TForm1.ComboBox1Change(Sender: TObject); 
begin 
  label1.Font.Name := Combobox1.Text; 
end;