Delphi – 如何获取Windows驱动器的总磁盘空间？

var
  Disk: Integer;
...
procedure TForm1.Button1Click(Sender: TObject);
var
  Total,Free: LongInt;
begin
  Total:=DiskSize(Disk) div 1024;
  Free:=DiskFree(Disk) div 1024;
  Gauge1.MaxValue:=Total;
  Gauge1.Progress:=Free;
  Label1.Caption:='Total size - '+IntToStr(Total);
  Label2.Caption:='Free - '+IntToStr(Free);
end;

procedure TForm1.ComboBox1Change(Sender: TObject);
begin
  Disk:=ComboBox1.ItemIndex+1;
end;