Can iPod software be installed on Windows 98 even though it says you need Windows 2000 or XP?
On another note, because the iPod is, as I said before, a mass storage device, Linux probably won’t have any problem reading its contents, and considering you mentioned Win98 you probably have a not-so-modern PC, and there are extremely lightweight and lean Linux distros that run easily on older hardware – I’d suggest Puppy Linux, which has a “LiveCD” version that runs entirely from a CD without touching your computer or Windows 98. You could boot off Puppy when you needed to put files in your iPod and then reboot back to 98, or you could “take the big step” and install Linux (Puppy can be installed).