Some laptops have a switch on the base of the unit which enables you to disconnect from the Internet. Could you check to make sure that's not the cause of the problem first of all?

I'm so embarrassed! When I checked that switch (after writing this question), it was indeed switched to off. But when I switched it to on, the wireless still didn't work. However, when I shut down and restarted my desktop, then the wireless network started working again. Thanks so much for your response!

You're welcome.

Could you please click the "Solved" button which will take this thread out of the loop.

Thanks.