Recently purchased an Inspiron Zino HD, Not very happy that Dell charges 30 dollers extra 4 Windows 7!

why is it that dell still includes windows vista by default on the dell inspiron zino hd and charges thirty dollers extra for windows seven? as i am a brand new dell inspion zino hd owner, i am not very happy that if i dont pay the extra thirty dollars to upgrade to windows seven home premium, i would have gotten stuck with windows vista service pack two home basic, an os that even msft admits that they made some serious mistakes while designing the os.