Hi My friend gave me Dell latitude E6420 laptop and he went to india. Now when I open it it lock with other user name and I reinstall Different OS like W7,W8,Vista, XP non of this work. It will install OS and When I install Driver and Update OS than It will changed setting automatically and come different file. It will logoff me and no more login again. When I install Ubantu it will run fine but it is new for me and don;t know any more if any body help me what can i do or how can i used it.