Right click on Network Neighborhood, go to Properties. And Window will appear that displays all network devices, connection settings, gateways and just about everything network. Just right-click on your 802.11b network card and click DISABLE.
Or if you really want to save the juice go into the BIOS and disable the entire interface to the WiFi card. Then it won't even show up under Windows, which means the entire interface to it is completely disabled so you're sure that no power is going to it. It makes the computer think that it's not even installed.