@Dietmar
On the topic of NICs, I have an industrial ETX carrier board that has a late revision Realtek 8168 chipset (Rev. 15) that I would like to try and get working in Windows 98 SE. It works just fine in XP with Realtek's XP driver but transporting that same driver over to 98 causes a BSOD in NDIS.VXD, and the 98 driver on Realtek's website just gives a yellow exclamation mark if I install it, so I'd like to try and make a win98 driver following your example.
Can you link me to the hardware documentation you've been using to make this these drivers?