WLAN is not on the PC, but on the laptop and mobile?

This morning was still the Internet on the PC. As I wanted to the Internet this afternoon, I saw that he is no longer connected to the FritzBox, which he is usually automatic. He also shows me the connections are available, but if I want to connect to the FritzBox, I should enter the network key, which I do not think otherwise. If I enter him then he sometimes closes the window and reopens it, then I have to enter the key again, sometimes he shows me that the key or passphrase is wrong or sometimes I have to enter a user account and password after I enter the key (there I do not know what an account and password I should enter there.) In addition, the Wi-Fi goes to my laptop and my phone as always only on my PC stop, please help, And am the way with a stick usually am PC connected to the Wi-Fi.

Did you download something the day before? If yes, what?

And please do not lie, then I can't help you: /

No I did not. And this morning it was still going on and since then I have definitely not downloaded anything

Already tried to go by Lan?