ICS is probably your best bet to share internet. You can install it using Windows 98 - it's a little tricky. What you will need is a network card in each computer and a cable to connect them directly or connect them to a router.
http://www.homenethelp.com/ics/ics-install-client98.asp
Installing ICS isn't as easy as setting up ICS in XP - but it's doable.
Good luck