To find the wireless security key that is on your computer go to the control panel and select Network and Internet, then next select Homegroup, then next select View and Print the Homegroup Password and the next page will have the wireless password.
Fine as it goes, Pure Evil but if the "Show characters" button wasn't ticked when the key was input for the first time, it will never show anything but asterisks and the button will be greyed forever after. There isn't really any substitute for going into the router's settings to fish to the security key.
As to the method inzone keeps posting, it shows only the Homegroup password which he seems to confuse with the wireless security key. It also applies only to versions of Windows that uses the Homegroup and again only to those systems where people allowed it to be set up in the first place.