Slightly confused as to what you actually have re' hard-drives. Perhaps you can/will post back with clarification (in case suggestionss below are inappropriate) - viz:
How many drives installed; what is installed on Master (and also Slave - if two drives); drive partitioning respectively; also format(s) of each drive/partition; also what (OS?) was on original Master drive - if now set as slave?
Meanwhile...
Your post does seem to imply that you have two drives installed; and that the Master is NT4 (and ntfs format - which is why the no fat16/fat32 error message...)?
Presumably a return to '98 only is the preferred option...?
If this is so then it's a delete the ntfs partition via the '98 boot-disk Fdisk util (ntfs shows up as non-DOS in Fdisk), then reconfigure/reformat of the drive back to fat16/fat32.
You can also use delpart.exe to delete the partition on Master, and then reconfig/reformat etc. for '98 - afterwhich re-install '98. (Boot-up with '9x/DOS boot-disk; change to delpart floppy and run util, following on-screen prompts.)
Delpart is around variously (download and transfer to a floppy, or add to a '9x/DOS bootdisk and thus avoid a floppy-change):
http://www.mesich.com
http://hercules.lss.ksu.edu/download/MSSTUFF/index.htm
and for Fdisk etc., and re-installing '98:
http://www.btinternet.com/~robert.bale1/formatinstall.htm
If there is a current Slave, and it has '98 already installed, then you could just reset that as Master, with current NT4 Master as Slave; afterwhich reconfigure/reformat that (Slave) NT4 drive as fat16/fat32?
As regards network/graphics issues: drivers may or many not be available for the NIC you have installed; similarly for the graphics card? Useful to first check if they exist for both items (web-sites for each item).
A NIC has to be manually installed in NT4; and also the required NT4 drivers for the graphic card. (Incidentally adding/installing a NIC is included in the help files for NT4...; as is updating a graphics driver...)
If you want to persevere with the NIC/display issues under NT4 (rather than go back to '98) - again post back?