If the printer doesn't have Windows 98 drivers, you're probably out of luck. Maybe create something that can take a PDF placed on the network, and automatically print it. Ubuntu is not lightweight. In my testing Ubuntu is pathetic on a machine with 256MB RAM where WindowsXP runs respectably. If you're on an ancient machine with 64MB RAM or 96MB RAM, Ubuntu won't work, while Windows 98 can still provide basic functionality.
I would dump the win 98 machine and if you reallly need to use Win 98 run it as a VM on the windows 7 computer.
Thanks for your answer! I already decided to remove Windows 98 and install Windows XP as a minimum on computers that had the problem. There was no way to connect Windows 98 and Windows 7 in the way that I needed .... Reggards