Is it possible to...

Ok, a not so general question here about networking...I have a westell 2100 dual connect modem which has two ports on it, one of the ports is for Ethernet connection and the second port is for USB connection. Well, I have two computers and I was wondering if it would be possible to Link one of the computers up to the modem through Ethernet, and have the second link to it through USB andif that would allow basic file-sharing, and LAN games...and possibly even have two systems online at the same time. So far, when I tried it all i got was one system on the internet and the other one getting a blank page as well as errors about a missing network cable..So anyone know if this possible or have any suggestions?

*The systems are: Win 98 & Win XP PRO
*Linksys lne 100 TX for both systems, though since 1 is using USB only one of those are using a NIC
*westell 2100 dual connect modem--DSL