Windows 7: Can't connect to wifi

Running Windows 7 Home Premium on a netbook. Since yesterday get message "Windows cannot connect to wifi". Running checks suggests resetting the router, but two other devices, an IPad and an almost identical netbook are connected no problem. I havn't changed anything. It can see the router. Done normal reboots, disconnect reuse connect adapter etc. no luck. This has happened before on two other computers on different routers, and we don't know what eventually fixed it, although changing the encryption method might have solved one of them, even though that computer had been connecting for weeks before the failure. The only one of our family devices never to have experienced this is the IPad. Help please.

If you can post a screen shot of the ipconfig/all from this machine it would be helpful.