There are two clients for laptops - a full client (which you probably are using) and a light client. The light client, GoBoingo, supports Vista and can be found at: http://www.boingo.com/download_goboingo.html. It is much smaller than the full client, only 800K total. You won't even know it's there until you enter a Boingo hotspot.

The next version of the full client will support Vista and will be released very soon.

Hope that helps,