|You'll want to try removing the saved Network Profile on your computer. It contains all the information your computer used to connect to your router via the old password.|
Go to your Network connections and right click on your wireless adapter and click Properties.
In the Wireless Networks tab you will find a list of your saved networks under Preferred Networks.
Locate and remove your wireless network. If you can I would recommend removing all of them. (This will require you to renter the WEP/WPA key for any other networks you previously had saved.)
Click OK and attempt to connect to your Wireless Network. Your PC should act as if it has never connected to it before.