Installing etherboot in Intel Pro/100 cards
An interesting page decribing etherboot is on the LTSP wiki, here.
Get the PROBOOT.exe tool from Intel. Read the instructions linked from that page, too.
Run PROBOOT.exe somewhere convenient.
Use "lspci -n" to figure out exactly which card you have.
Use the ROM-o-Matic to create a new Etherboot based ROM image. Download the image and save it somewhere. Rename it as detailed in the instructions at Rom-o-matic so that it can be used with fboot.exe.
See also [1]
Then you load the fboot.exe and new ROM image into an MSDOS boot floppy.
Boot the machine with the Intel card from the floppy.
Use File:Fboot.exe (which is part of the ProBoot.exe kit) to flash the new image into the card.
Reboot the PC, enter BIOS setup mode, and configure it to boot from the network card. Save changes and exit BIOS. The system should now boot from the card.