i tried solving this problem 2 days by myself, trying all method that i got from some forum including from here and got nothing >_<
and i called microsoft technical support (stupid, i didn't do it since begining ^^), and it solved!! the guy from microsoft said, it is because of the internet connection, maybe some provider settings (firewall, proxy, etc) bothering the instalation, he asking me for change the internet connection, and done, i can update it to 8.1
so, i suggest you all that experience this problem, call microsoft, it is the best way for solving it :D