networking

You need a broadband modem capable of making an ethernet connection (one that can only connect with USB will not work).  You will also need a wireless cable/dsl modem and a wireless network adapter in any computer that you want to connect by wireless.  Nearly all cable/dsl routers will also allow up to 4 computers to be connected by wired ethernet.

For security, you should use WPA encryption.   Some good articles on wireless security can be fround at:

http://www.microsoft.com/windowsxp/using/networking/learnmore/bowman_05february10.mspx

http://www.ezlan.net/Wireless_Security.html

http://www.pcmag.com/article2/0,4149,1277020,00.asp

Steve

Yes, you can do this, but it gets quite complicated.  You will still need a wireless router and you will have to set up the router to run in "Access Point" mode.  You will need a second computer that connects to the internet through dialup and that computer will need an ethernet network adapter to connect to the router.  On that computer you will have to enable internet connection sharing on the dialup connection.  You will also need to assign a static IP address to the wireless card on the computer that is going to be sharing the internet connection through the wireless router.

Steve