The easiest way to do this, is 1) Buy a wireless router that is compatible with your modem and your pc. 2) Buy a wireless network card for you laptop / other pc 3) Configure it.

Some Broadband modems aren't compatitble with certain routers and vice versa, I would reccommend spending a lot of time researching this out before making a purchase. If you have a cable modem, then I would reccommend this http://www.ebuyer.com/customer/produ...duct_uid=45023