Posting to c.o.l.s because machine runs only Linux, to a.s.p.c because
it's clearly a Compaq firmware issue, and to c.o.l.h because the
firmware might
as well be hardware, since I don't (yet) know how to change it.

This problem is not for the faint of heart. I have read the manuals on
the Compaq
website, tried the obvious remedies (see below for gory details) and
they haven't
worked. My other Linux machines work just fine :-)

The Problem Machine is one of the Compaqs from about 1997/8 without a
"real"
BIOS. It's a compact desktop Pentium II 233Mhz 96MB 2.1GB+2.4GB.
There is
no obvious way to tell its exact model number, but at boot time the
screen displays
"Deskpro 4000", a category containing at least 20 models.

When I installed Linux on this machine, it had its original HDs which
had been used for Windows 9x. I deleted the Diagnostic/ Setup
partition,
not knowing any reason not to :-), repartitioned and reformatted for
Linux.
There was no problem - Linux booted fine from the first HD or floppy or
CD.
When I wanted more HD space, I replaced the first HD (HD0, or /dev/hda)

with a known good one containing a bootable Linux, and also replaced
the
second HD with a larger one. (The first HD is now a Maxtor 10GB, and
the second a Western Digital 10GB. I mention the manufacturers because
I have heard rumors of boot-time incompatibility of certain pairs of
drives, but I have no definite info. 10GB is also , I think, greater
than a magic number - 8.x GB? - in certain kinds of BIOS firmware.)
There are no MSDOS or Windows partitions.

Now the Compaq firmware won't boot from the HD ("1790 - Disk 0 error"),
and it wants me to run the Compaq setup utility (at one point it
displayed
"If you are running Unix, you still need to use the Compaq utility to
configure
the hard disk").

The new first HD is in fact present and functioning, because I can boot
its active partition from a SmartBootManager floppy, or mount, read and
write it when booted from a Linux CD. No problems with the second HD
or the floppy drive either, once booted. So I didn't _obviously_ botch
the
hardware replacement, though there may still be something subtly wrong.
The new first HD was the first HD of two on the same controller in its
previous machine, and also in its current machine. I just left its
jumpers
as they were, though I have no key for how they should be.

OK. I downloaded the self-extracting archive sp8126.exe (PC Diagnostic
and Setup Utilities) from the Compaq website, verified it using unzip
-vt
on another Linux machine and ran it under dosemu (because I don't have
an
MS machine). The resulting 2 setup/diagnostic boot disks will happily
boot to menus on this other machine, but on the Problem Machine, they
each just give "Starting MS-DOS" followed by a hang. FWIW, soft reboot
(shutdown -r now) also hangs (and always did) under Linux on the
Problem Machine even if I've booted from a CD which remains in the
drive.

The floppy drive is OK, because I was able using the "other" machine to
create two different bootable floppies (FreeDos and SmartBootManager)
which successfully boot on the Problem Machine.

I found an apparently similar case on the net where someone claimed
that the problem could be solved (and the setup utilities could be run)
by moving the floppy drive to "the other connector on the ribbon cable,
the one without the twist". On the Problem Machine, there is no such
other connector, and never has been, and if there were, it is not clear

how it would help, because it would presumably move the floppy drive
to the B: role (/dev/fd1), which is not supposed(?) to be bootable at
all,
whereas I can currently at least boot SmartBootManager or FreeDos
from A: (/dev/fd0).

I'm fairly indifferent about actually restoring the setup partition,
since
Compaq says the setup can be run from floppies, and I don't expect
to need to run it often; but I would _really_ like to be able to boot
the Problem Machine from its present HD.

Any clues will be much appreciated.

-D