You may find you are on the network, but not on the internet, the things I did that helped:
Turn off computer, modem, and router.
If separate router and modem, make sure they are away from each other, make sure they are not near a microwave or other radio wave device.
First boot your modem, then after a minute boot your router, then your computer.
Make sure you disable any other networks in my network place that are not being used, and that the router drivers are up to date.
If you have third party wireless controlers with the drivers, try using these and do not let windows control the network.
And finally, make sure it is your network you are logged on to, and you are not picking up a neighbors by mistake, signal strength is paramount.
Edit: you may need to do the reboot thing after making any software changes.
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