I have the same problem,same dsl modem speedstream 5200 and I'm try to get ethernet working on a Dell inspiron 4100 laptop as well as on my desktop.
on the desktop I connect the modem to the USB port and the USB light on the modem lights up properly, but then I don't know how to set it up.
I'm a total linux newbie (needless to say).
how would I go about setting up the connection?

thanks CM