If the Wi-Fi stopped working on your laptop after you upgraded it, it is possible the problem is a missing software driver
Anecdotally, at least, it seems that lots of people have had problems with the Wi-Fi connectivity of laptops and PCs after they have been upgraded to Windows 8. One reason for Wi-Fi problems in Windows 8 is the lack of up-to-date software drivers, as our Helproom Editor explains.
QUESTION I've just upgraded to Windows 8 on my Toshiba Satellite L750. However, I now have a problem: Toshiba said my laptop was ready for the OS, but following its installation the Wi-Fi no longer works. I suspect that the driver doesn't support Windows 8, and Toshiba was unable to provide me with a newer version.
HELPROOM ANSWER These may, of course, have been added since your conversation with Toshiba, but there are in fact Wi-Fi drivers available for your laptop on Toshiba's support site. However, two types of driver are offered – one for an Atheros wireless adaptor, and another for an Intel model. You will need to ensure you install the correct version for your specific model's specification. If you can't easily find out which adaptor is installed, it won't hurt to try both and stick with the one that solves your problem.
You'll find the driver download page at the Toshiba Laptop Driver Downloads page. Select your laptop specifics from the drop-down menus, and be sure to select ‘Windows 8 – upgrade' as the required operating system.