Tips

Find Wi-Fi password stored on your PC
I haven't tested any of these because I run Win 7 under Parallels on my Mac
and they don't seem to work there.

 Control Pannel > Network and sharing center > click on the WiFi name >
  a new window will open, select wireless property > security >
  show password. And that’s it, here is your WiFi password in plain text
 
 Control Panel\All Control Panel Items\Network and Sharing Center
click on connected device
Wireless properties > Security > show characters

Simply open up the cmd and type in the following command.
netsh wlan show profile WiFiName key=clear