Hello,

I recently installed NetBSD-1.6 on a couple different models of older
Compaq notebooks: 

Contura 420C       - 486/75Mhz with 24Mb RAM and 1Gb HD
Armada 1550DMT - Pentium/133Mhz with 80Mb RAM and 4Gb HD

No substantial problems were encountered.  All hardware I attempted to
configure and use is working with no great challenges, though a few
little problems surfaced and some simple tricks were learned. Here is
more detail on each model:

Contura 420C
-----------
This is a common as dirt 486/75Mhz machine readily available in good
working condition at eBay for about $50--much less if you take a chance
on a fixer or a, 'I don't have a power cord and don't know if it
works...' item ;)  Besides the slow (by today's standards) CPU, the big
drawbacks to this model are A) The lack of any sound capability (beyond
the standard PC speaker), and  B) A 32Mb absolute hardware limitation on
RAM (this was pretty typical on most 486 era machines). Otherwise, this
is a great little beast with tons of uses, like ad-hoc surfing and email
at the kitchen table or your local Starbucks, wardriving and site
surveying, and portable/demo/test servers of apache, mysql, or whatever,
to amaze your friends, family or potential clients...

It has the common arrangement of two PCMCIA slots, but only one will
take a Type III lan card such as a 3Com 3C589 or any WaveLAN cards.... 
There is a built-in floppy, an external keyboard/mouse connector (PS/2),
1 serial, 1 parallel, and an external VGA port.  There is a connector
for an external docking bay, but I do not own one of those. It uses an
external power supply. The batteries are still available from several
internet sources, typically around 50 or 60 dollars for a new one with a
warranty.  I have a couple of used ones that give me about a half hour
charge, and I bought one new one for 50 dollars that lasts about 4
hours!  I have 3 of this model notebook, configured almost
identically(all on NetBSD-1.6), that get a lot of use here at my home
and on the road...

NetBSD-1.6 installed on this model the first try, using the laptop
diskette images and a Lucent/WaveLAN Silver PCMCIA Card (/dev/wi0),
getting the distribution from a local server I have setup to mirror the
NetBSD binary sets.  I have since also installed using an
Avaya/WaveLAN Gold wireless (/dev/wi0) and 3COM 3C589 (/dev/ep0) with no
problems.  Another slightly less critical drawback to this machine is
the fact that XFree86 v4.x DOES NOT SUPPORT the video.  This is
docemented at www.xfree86.org, but it took me a couple days to find
that. So, do yourself a favor: when you install, be sure to NOT install
the standard X binary sets for NetBSD.  If you want X, then after the
initial install, get the XFree86 v3.3.6 binaries from here:

ftp://ftp.netbsd.org/pub/NetBSD/arch/i386/XF86-3.3.6-1.6_BETA2

Then from the root directory, do a 'tar -xpvzf PATH_TO_X_SETS/x*.tgz'

You will also need a good XFree86 v3.x config file.  Here is the one I
use on all three of my 420Cs:

http://digitaldowns.com/download/Compaq-Contura-420C-etc-XF86Config.tgz

This will let you run in 640x480 at 8-bit depth.  Not exactly lighting
the world on fire, but it's better than nothing!

And, since this machine has a tiny RAM limitation, I strongly advise
creating a custom kernel with all the fat trimmed. Here is a kernel
configuration file I use, but be warned, it trims A LOT OF STUFF you may
want to put back into it (like nfs, linux emulation, etc.)...

http://digitaldowns.com/download/Compaq-Contura-420C-kernel-config-YAVAPAI.tgz

The config file extracted from this will be called YAVAPAI.

I have not tried to use the external serial, parallel or video ports. 
The floppy drive and external mouse connector worked fine, first try. 
On some machines you can use the external mouse and the built-in
trackball at the same time, but on this one, when it boot with the
external mouse connected, it disables the trackball.  No problem, I
hate the trackball and use a real 3-button mouse--whoohoo! 

The apmd daemon works pretty well.  I can 'apm -S' and 'zzz' to sleep it
and it generally wakes up nicely.  Often times the hard drive wakes up
with a single 'soft error (corrected)' type of message, but this seems
not to be a serious problem.  Other times, if the wi0 card is busy at
the time I force sleep it, it might wake up with some network errors,
sometimes recoverable by just waiting for it to sort itself out,
but occasionally the network card is munged and I need to reboot to get
it working right again.  So, I generally just try to be sure and put it
to sleep when I'm not actually transferring any data, okay? :/

I feel I should point out that I tried to install FreeBSD and Debian
Linux (both of which I have experience with) onto this machine and
neither of them were pleasant experiences... Lots of installation
glitches and PCMCIA and other driver problems. Overall, I'd say
NetBSD-1.6 is a GREAT choice of OS for this notebook.

Armada 1550DMT
--------------
This is a very solid Pentium/133Mhz machine.  I have two, each with
80Mb RAM and 4Gb hard drives.  The 12" TFT displays are
both REALLY EXCELLENT despite being several years old.  You should be
able to find a good, pretty complete one on eBay for around$150, maybe a
bit less after xmas ;)  Much of what I mentioned above about the Contura
420C can be applied to this machine. It has all the same hardware, plus
better video, built-in soundblaster-compatible audio and a pair of
decent speakers, a built-in CDROM drive, and a built-in modem, and
TA-DA!!! -- a built-in power supply!  Installation via wireless was just
as easy as for the 420C mentioned above.  Configuring a kernel to
support the additional devices was easy too. Everything worked as I
hoped. Here is a sample kernel configuration for it that I use:

http://digitaldowns.com/download/Compaq-Armada-1550DMT-kernel-config-THISTLEDOWN.tgz

This should expand into a kernel configuration file called THISTLEDOWN.

The biggest chore in getting this model running as a client was tracking
down a good XF86Config file, as this one has a different video system
internally than the 420C.  As it turns out, even though the video
chipset in this model is listed as supported at www.xfree86.org, I had
trouble getting it to work.  So, I just did the same thing as with the
Contura 420C: skip X binary sets on the install, and manually put
XFree86 v3.3.6 on the machine...

Here is the XFree86 v3.x style XF86Config I use for these machines:

http://digitaldowns.com/download/Compaq-Armada-1550DMT-etc-XF86Config.tgz

This sets up your choice of 800x600 or 640x480 in either 8 or 16 bit
depth.

Like the 420C, you can plug an external mouse into this computer and it
should work fine with the above XF86Config... however, the built-in
touch-pad style mouse and buttons will also work simultaneous to the
external mouse... nice...

One thing I have not tested is the built-in modem.  I understand it's a
33.6 kbps by default, and _might_ be upgradeable to 56k by a flash rom
upgrade, but I have no need for my models to use a dial-up, so I haven't
mucked with any of that. 

Apmd does not seem to run right on this box, conflicting somehow with
bios-based power management.  The sample kernel above turns apmd
support off in it, since I can't figure out how to resolve the
problems/conflicts.

As for the sound system, I found using the built-in soundblaster and the
CD player no more difficult on this machine than on a typical modern
desktop running NetBSD (that is, it's not quite as plug and play and
easy as on _some_ operating systems pre-configured for you at the
factory in just the right way to get sounds out quickly, but it works
without much trouble after you've got a proper kernel config and some
decent packages installed)...

Here are some of the packages I've managed to install and use on this
notebook with no major headaches:

perl  python  links  icewm
enlightenment  windowmaker
mozilla  galeon  xmcd  xmms
gtk-gnutella  gaim  sylpheed
xstella  apache  mysql  xchat
net-snmp  nmap  wistumbler
...and many, many more...

Of course, with the small RAM capacity and modest CPU oomph, I do not
recommend actually using Mozilla, you just need it to run Galeon ;)