Excerpt from Matt London:

     The problem is the only space I have to put it ATM is on a SCSI drive,
   and my scsi card has no bios, so I can't boot from SCSI. So, no problem
   thinks I, and I've got a 60M partition on an IDE drive (wd2g). Now, the
   problem is, how do I set things up so it can boot from there, and then
   pull the root fs from sd0a? ATM I'm booting with the install CD to pull up
   the bootloader (I can't be bothered finding a disk ATM), then running boot
   wd2g:netbsd -a and specifying sd0a when it asks for root. Not really an
   idea solution :&)
(snip)

Maybe you could try DOSBOOT?  That would require the kernel to be on a
DOS-readable disk or partition.  You don't say what file system is on wd2g.  I
don't know how big your NetBSD kernel is, whether it would fit on 3.5" 1.44 MB
diskette.  I am more familiar with LOADLIN, which is used to boot Linux when
running DOS.