How do I list users and change their passwords?

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http://crunchbanglinux.org – Hiya, newbie question.I bought this laptop from my dad with #! installed already, I know that he's still got a user account on here and I want to change his password. I don't want to delete his account on the off chance that I brick the netbook somehow. So I need the command to list users, change user passwords.Also, I would like to know how I would go about disabling any keyloggers or password saving devices that he may have enabled while it was on the laptop.For the record. I'm just paranoid, not trying to lock my father out of his own laptop or something @_@ (HowTos)