No subject

> One more thing -- top tells me I have swap space (313M), but it's not
> used at all - is that odd?  I just rebooted and ran top. Machine hung,
> but at least I have some output from it... 

Very strange.
First, even if 313Mb swap is an unusual value, there is nothing wrong
about it. Swap not being used is not odd, it's good news, meaning your
memory consumption is less than what you have in RAM (memory chips).
But, having the machine hanging after a reboot on totally common
operations is highly critical.

This even sounds to me like an old 'CPU fan error' : the processor's
fan doesn't cool the heatsink enough and the CPU 'freezes' when the
temperature high watermark is reached.

[...]

'top' output seems quite correct for such a machine.

> Thanks for your help so far - I feel like I've been set down on a
> strange planet with this machine.  (I'm used to much newer servers, so
> this is probably a good learning lesson for me - okay, so this isn't
> *that* old, but still...).

No problem, we're here to help ;)

Now, my diagnostic would be : hardware failure.
I'd say this machine never was stable, be it because of a motherboard
flaw or some on-board chip not being recognized and crashing
unexpectedly. 
Usually, the linux kernel writes some output on the console on a
software crash or on a hardware triggered kernel crash. That may lead
you in some direction.

You may test a live cd on it, that should quickly (especially with
knoppix) tell you if things should be running fine or not.
If knoppix boots and lets you play, then it's just the Debian setup
that's outdated and you may try refreshing it so you get the latest
kernel fixes for the drivers you need.
If knoppix crashes also, it would confirm a hardware issue.

This may not mean the hardware is 'faulty', it may just be an
incompatibility, even if I doubt it.

You may try entering the bios and reset all settings to defaults,
sometimes there even are profiles such as 'safe', 'performance',
'extreme' ... 

If there is data you absolutely need on the machine, unmount the hard
drive, plug it elsewhere (there are some very nice ide/ata-to-usb
adapters) so you may grab your data and play with other, newer,
distros.

Now, I'am afraid, unless you're in the Paris/France area, I may not be
able to diagnose things further ;)

Read you soon,

R. Daneel Olivaw,
The Human Robot Inside.