I wouldnt of thought it would directly be a hardware issue, its probably a driver issue, windows 98 is 8 plus years old now, and in computer years thats a long time.
Microsoft stopped supporting windows 98 back in 2002 or 3 i think, so its not suprising that hardware vendors will stop supporting an operating system that very few people use, in terms of vista, vista will support your board when the drivers catch up, if infact they havent already.
I dont know for a fact but i wouldnt be suprised if windows 98 doesnt support your board.
Vista will certainly support NF4 boards.
Its not a case of the board talking to windows, its a case of windows talking to the board, windows will undoubtable have some interaction with all hardware installed. Drivers enable the hardware/software interfacing, and its probably just a case that there are no drivers that support your board under windows 98.