authentication password forgotten?

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http://askubuntu.com – I don't have a log in password. But when I want to install any software or update it demands an authentication password which I don't know at all. I tried to reset it by using recovery mode, but when I type passwd USER which is my only account name it says that user "USER" does not exist. And when I type passwd it shows type a new password but I cant write any thing. I need help please !! (HowTos)