After installing Windows 8.1 on my wife's laptop it would not connect to wifi or the internet. The computer kept saying "limited" connectivity and none of the built-in troubleshooters could fix the problem. I reset the router numerous times, rebooted the computer, updated everything, reset the TCP/IP stack, etc. In the end, the problem was that while installing 8.1 Microsoft removed my wireless adapter drivers and replaced them with a new Microsoft version! Argh!!!! What the hell?
Reverting back to the manufacturer's drivers solved the problem.