Go to Control Panel and Network and Sharing Centre.
On the left, click Manage Wireless Networks:
Then click on your Wireless Network and select Remove.
On the Confirmation Box, select Yes:
Repeat this for every Wireless Network you have in Manage Networks.

Warning
You will lose your Network Key, so if you do not know it or it does not say on the router. Follow this.
Click Wireless, Right Click on your Network and select Properties.
A dialogue like this should open:
Click Show Characters and click Yes to the UAC Prompt:
You will now see your password:
If this fails, I would try reinstalling your Network Drivers