Thanks to Martin Husemann, Dave Huang and Soren Jorvang for suggesting
that himem.sys is getting in the way of loading the kernel with
dosboot.com.  I've now learnt far too much about PC's and DOS in the
last day or so, and can now go back to plain ole NetBSD, whilst also
keeping the powers that be at work happy that I haven't wrecked their
machine :-)

Thanks all.

Simon (who still prefers DECstations for ease of configuration)