Windows Vista will include a nice Network and Sharing Center that lets you configure whether individual wireless networks are at home (and thus trusted), at work (also trusted, but usually configured differently), or public (a wireless AP at a café, airport, hotel, or other public space where you don't want other users to access your PC's files). But you don't have to jump into a time machine and run Vista to be secure on the road today. Users with Windows XP-based notebooks can still be secured for public Internet access if you're willing to follow a few common-sense rules.
First, be sure you're logging on with a password. Without a password, virtually any cyber thief worth his wireless card will be able to jump onto your PC quite easily.
Second, make sure you're using a good firewall, such as the one that Windows XP Service Pack 2 (SP2) offers. This software will let you prevent incoming network connections, which is helpful, although you'll have to configure it manually. To do so, locate the Windows Firewall utility in Control Panel and turn on the option titled No exceptions. Just remember to turn it back on when you're back on a trusted network.