You cannot add Nics to the Microsoft (3com) RIS Boot Floppy, However
there are third party vendors that sells ris boot floppys with
additonal nic support.
Is it not possible too boot from the PXE boot ROM on the NIC or doesnt it have one - this way you can just add your drivers to your RIS image and the txt .sif answer file and bob is your preverbial uncle. Its simpler and cleaner than messing around with floppies
Worked like a charm when i set it up, one thing if your using 2k3 server get the latest SP before even bothering