>56 MB ram, boots into hp-ux, then immediately
gripes about something
 >missing, gives a return code of 256 and dumps memory to the hard drive
 >(will repeat endlessly too). 
If you know the magic incantations you might be able to get into single user
mode.  Have you tried this?  It's fairly easy to do this on a Sun box, but
as I recall it's a royal pain to do this on an HP.  Unfortunatly I've no
idea where my notes on this might have ended up.
  I have never had a hand on HP-UX but when I first got
my MV4000 it very
 much the same thing as your UX box.  The fix was the run a filesystem
 fixer.  While I was at disk stuff I ran the high-level formatter, scanned
 for bad sectors etc.  Came right up.  It tortured me for like two weeks
 before I figured out it needed this and how to run the checker when I
 could not boot the machine.  There was a mechanism to execute a single
 file from the filesystem without mounting it so as not to lock the disk
 against the checker.
 Else you could get a maintainance build of HP-UX on floppy and check it
 that way.  Maybe Linux FSCK can handle your disk format? 
GOOD GRIEF NO!!!  I would guess the Linux 'fsck' would refuse to do
anything, but if it doesn't all it could do is make things worse!  *DO NOT*
run versions of 'fsck' against filesystems other than what they're intended
to be run against!!!
                        Zane