Wireless Connection lost

Just last week, both my Dell with Vista and my boyfriends Dell with Vista stopped being able to connect to the internet wirelessly. I also tried at my parents and it does not work. I checked my configurations and it states that our media is disconnected as well as the wireless card and adapter. How did that happen? How can I fix it? I need to get school work turned in and this is a royal pain in the rear. My step-daughters laptop still connects, she has a mini dell with ubuntu (kids software and games). Please help.