Trust me when I say it'll be better for him, and he'll see better speeds, if he just goes out and picks up an ethernet card. They are damn cheap.
Here is a list of them from newegg:
http://www.newegg.com/app/ViewProdu...property&DEPA=0
The cheapest they list is $5+$3.99 shipping ($8.99), but he should be able to head down to a local computer store and get one for the same price (and I don't mean BestBuy)
CompUSA has one for $8.86
http://www.compusa.com/products/pro...3697&pfp=BROWSE
They also have a D-Link 5pack for $30. Use one and sell the rest for $5-10 each and make his money back or close enough.
Trust me on this. Using the USB is a bad idea. I've not heard from people using cable and dsl modem connected with USB that they either end up having to reinstall the USB drivers every few months/weeks/days or even everytime they shutdown or restart.
Plus I've also proven with a number them that switched to the ethernet card that they do in fact get much better speeds.
If his modem is strictly USB, tell him to call the ISP and ask for a replacment that supports ethernet.....if possible even demand one that does.
I don't care what anyone says about USB being 12mbps, it's only one-way...plus the cable/dsl modem are only 10mbps anyway and the ISP is only putting out 1-5mbps (as the case may be) so it still doesn't matter if USB is 12mbps. It just wasn't designed for hardcore networking, however it is nice for quick, short and dirty networking between 2 machines.