That's funny, now it works! I'm not sure what did I do wrong in my previous test. The only difference I know is that then I did 'cd /' before '/etc/mkfs /dev/rp3 153406', and now I have skipped 'cd /'.

Aaaah, nice to be able to use V7 Unix on modern computers =)
        PDP-11 simulator V3.8-1
        Disabling XQ
        boot
        Boot
        : hp(0,0)unix
        mem = 177344
        # RESTRICTED RIGHTS: USE, DUPLICATION, OR DISCLOSURE
        IS SUBJECT TO RESTRICTIONS STATED IN YOUR CONTRACT WITH
        WESTERN ELECTRIC COMPANY, INC.
        WED DEC 31 19:08:26 EST 1969

        login: root
        Password:
        You have mail

I don't see a '@', but otherwise it works now ^^. Now I'm going to play a little, add new users and fix the time zone =). Thanks for all!