Whenever you connect to a new wireless network, Windows XP adds it to a list of preferred connections. Over time, this list can get cluttered with entries, at least some of which are in the same geographic location. You can easily end up connecting to the Beantown Wireless Network when you thought you were connecting to the Quincy Market Hotspot.
WinXP creates the list, but you can control the order of preference. You can also determine whether your computer should make an automatic connection. Click the Wireless Network Connection icon in the System Tray. In the Wireless Connection Status window, click Properties. Next, you want to select the Wireless Networks tab. The order of the entries in the Preferred Networks list controls the order of preference when multiple networks are available. Click a network to select it and then use the Move Up or Move Down buttons to change its position.

Occasionally, the circumstances may dictate that you don't use a preferred connection. To prevent WinXP from automatically connecting to a preferred network, click the network to select it and then click Properties. Select the Connection tab. Remove the check mark next to Connect When This Network Is In Range and click OK.