Go the wireless route - a lot less hassle and probably cheaper too.
You just need a USB Wireless dongle for each pc. One of these will be fine:
http://www.savastore.com/productinfo...=0&rstrat=7833 I bought one to go with my laptop as it was less than a tenner on special, and it works a treat. I can even use it when I take the laptop round to my old man's, and connect to his Wanadoo Wireless broadband that he signed up to, as this included the wireless modem as part of the package.
You can connect as many wireless computers to it as you want, and a computer via an ethernet cable too.
He finds the Wanadoo service fine, and it was cheap when you include the price of the wireless modem.
As long as all of your PCs have a USB connection, you should be fine.