Excerpts from netbsd: 13-Aug-97 Re: NetBSD 1.2.1 bootblock .. Bill
Squier@guinness.cs. (1281)

> Here's the disktab generated by the install script:
> 
> WD730|NetBSD installation generated:\
>         :dt=ST506:ty=winchester:\
>         :nc#1416:ns#63:nt#16:\
>         :se#512:\
>         :pa#1242864:oa#0:ta=4.2BSD:ba#8192:fa#1024:\
>         :pb#184464:ob#1242864:tb=swap:\
>         :pc#1427328:oc#0:\
>         :pd#1427328:od#0:

Offset 0 is wrong, at least if you use a boot selector.
I suggest the following:
1. Use pfdisk (the DOS program) to get BIOS' opinion of the
  disk geometry.
2. Use NetBSD fdisk to create a NetBSD partition that begins after
  1 track (will be offset 63 in most cases). Make sure fdisk has
  the right idea about the BIOS' disk geometry
  before. Use device /dev/rwd0d.
3. Proceed as usual with disklabel and installboot
   (device /dev/rwd0a).
4. fdisk/mbr (under DOS). If it doesn't boot, install os-bs.

best regards
Matthias