Windows 98 was never really friendly with USB flash cards or any kind of removable media... Usually you would have to hunt down some kind of driver initially, much like you put the Amiga 1200 with fat95 files, kinda like a driver to read them. :-)
Chances are that Windows XP would have immediately detected it and added it.
I would just try to find the driver to that pcmcia card you are using and go from there.
