You need to set up an ad-hoc connection. Read this then click the link at the bottom.
"Usually a piece of hardware called wireless broadband router or access point is required. In this tutorial we will teach you how to setup a wireless network without this device, allowing you to save some bucks. However, you need to know beforehand what are the disadvantages of not having a wireless router:
-The only encryption scheme supported in Windows XP is WEP, which is not secure: a hacker with the right knowledge can have access to your network. Thus if you are building an ad-hoc network the way we are describing the host computer (the one with the Internet connection) must be running Windows Vista or greater so you can enable WPA2, which is a secure encryption system. The client computers can be running Windows XP, this requirement is only for the host computer.
-The computer that has the broadband Internet connection will need to be always turned on. If you turn it off the other computers will lose their connection to the Internet.
-Your network will be less safe, as broadband routers integrate a hardware-based firewall.
-Your network speed will be limited to 11 Mbps, even if you only use 54 Mbps or faster cards on your network."
then read this page
http://www.hardwar...dband-Router/418/3