This will show you some information like your IP address and the "renew" will try to renew your IP address by doing the same thing that happens when you restart.

winipcfg.exe

This brings up a little box that shows IP info and if you click on "advanced" you will see even more info and you can see how many network devices windows thinks it has.

I just thought I would mention these, they always came in handy.

In Linux you want to install "tcpdump" if you don't have it try

urpmi tcpdump

and urpmi should find it on your distro CDROM. tcpdump will show you activity on eth0 (your ethernet interface) and you can watch the packets fly to see your computer talking to the DHCP server etc..

Try this (as root)
tcpdump -Xs 4000 -i eth0

read about netstat
man netstat

I am not sure if you can bind the NDIS with USB in Windows 98, natively.

Make sure to check your IRQ's. It could be a case of the 'too much sharing one IRQ' blues. If you can find out which IRQ the modem is trying to use during install, then you can search for other devices that might be sharing. If the device is a modem or sound card in a PCI slot, you can attempt to move the devices to other PCI slots to change assigned IRQ numbers. Then attempt reinstall.

The IRQ problem seems to match your discription of the problem most closely. If you already have a network card installed, please consider using it as the solution to your problem