tool to convert /etc/passwd and etc/shadow

i wonder if there is a tool to read the /etc/passwd or /etc/shadow files in order to reset user accounts to the same one.
By moving (restore) all filessytem and data to another same Sun box, none of the users are able to logon to the new box which i didn't change nothing. But if i reset the user password, they can logon to Sun Solaris 9.

Thanks

Check pwconv(1M)