Of course you can. Just make sure any card you have has drivers for 98se and many if not most will. Won't be the fastest machine but your only talking about 20 or 30 Mb transfer rate anyway. Something that even a slow 2.5" older laptop drive will easily sustain. It's been awhile since I've installed wireless cards on something that old but I've installed hundreds on systems with similar specs and 95. The ONLY concern you have is getting drivers. other than that your fine.
What you might consider though if you want a bit better overall performance is running linux on that machine. You can download and run Knoppix right off the CD so you don't have to install the OS on the drive and you can play around with it and see how you like it. You will still need enough ram to run smoothly and with a laptop that old it might be hard, or not worth the money, to upgrade the memory if it has say, less than 128 MB.
Oops, just saw it had only 40 MB. You'd have to price it to see if it is worth it. Will still run the OS you have on it though, with wireless connectivity, again as long as the card has drivers.
<P ID="edit"><FONT SIZE=-1><EM>Edited by kwebb on 01/31/05 08:31 PM.</EM></FONT></P>