取得磁碟剩餘空間

var
  g_sTempDriver : integer;
  DiskFreeSize : int64;
begin
  g_sTempDriver := Ord(UpperCase(g_sTempPath)[1])-64; //UpperCase(g_sTempPath)[1]某個槽
  DiskFreeSize := DiskFree(g_sTempDriver);

  //DiskFreeSize div 1024 = bytes