Filseclab Personal Firewall Professional Edition
Full user review
"It does work with Windows 98"
It was the only free program I found that worked as a firewall for Windows 98.
I had a probem with it freezing up the internet permently until I uninstalled it.
If you have to have a firewall, then you could use this. It was just too troublesome for me because I don't use window 98 much for the internet.