steps for a simple and driver-free wired and wireless network:
1. get rid of the usb aDSL modem/connector. Get your telco or provider to swap it for an ethernet-based one.
2. get a router (linksys, et al.) that has both ports and wireless capability (802.11b or b & g).
3. connect ethernet aDSL modem to router. Configure router.
4. connect all computers--two wired PCs, one wireless ibook--and they will all be on the same LAN (your router), sharing the same connection (aDSL).