WirelessKeyView is an excellent tool that will help you recover any password or wireless key you have lost or forgot.
This effective tool will get through your network and find this keys (WEP and WPA) that are stored in your computer by a services pre-installed in your Windows Operating System called -Wireless Zero Configuration service-.
It will create a list with all your saved passwords and keys and save it in a text, html or xml file.
This is an amazing application and you won't believe it but it's absolutely free.
Just download it and try it, You will be amazed by its functionality and effectiveness.