[ubuntu] can't login after installing samba(?)

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http://ubuntuforums.org – hi, i was trying to share folders between my ubuntu 12.10 and a winxp. tried to install samba and got an error (package name was samba4, btw), and a suggestion to remove a certain file (which i shouldn't have,but did...). during the same session i also changed my workgroup from WORKGROUP to HOME. after restarting my ubuntu i can't login to any user account! :-( when entering the correctp password i get "invalid password" instantly. (when i enter wrong passwords ubuntu takes some time to think about it and then rejects them.) i tried doing passwd username in recovery mode, b (Hardware)