A few more things to try...
Try logging in as SYSTEM with passwd MANAGER or, if that does not work, try FIELD with passwd SERVICE .. this might work (these are supposed to be undocumented outside DEC, but you know how things can slip
If that does not work...
What you need to do is do a conversational boot and give control to the
console instead of the system startup procedures. Then you rename the
system's username/password file and replace it with a Digital-supplied
template file instead. This file has a known SYSTEM password.
How-to (assuming DUA0 is your system disk):
Press the halt button if needed to get to the >>> prompt
>>> B/1 DUA0
SYSGEN> SET/STARTUP OPA0:
SYSGEN> C
... some messages are displayed ...
... you get the dollar prompt ...
$ SET NOON
$ SPAWN
$ SET DEFAULT DUA0:[VMS$COMMON.SYSEXE]
$ RENAME SYSUAF.DAT SYSUAF.OK
$ COPY SYSUAF.TEMPLATE SYSUAF.DAT
$ RUN OPCCRASH.EXE
... system halts ...
Press the halt button if needed to get back to the >>> prompt
>>> B/1
SYSGEN> SET/STARTUP SYS$SYSTEM:STARTUP.COM
SYSGEN> C
... system boots into the VMS equivalent of multiuser. You may get some
error messages if the system tries to start layered software that relies
on accounts that are no longer available.
You can now log in as user SYSTEM with password MANAGER (case un-sensitive).