How to find wireless network security key

You don't know where your own wireless key is did you not record it somewhere assuming you made it or was supplied by your isp?

Have a look in your router or in your network settings on your computer.
 



I set it 2 years ago. I just received a Lenovo B570 as a gift. I am having all kinds of problems setting up wireless. And no, I have no idea what what I used.
 

It belongs to me. I set the key 2 years ago and have mis-placed it, I just received a Lonovo B570 as a gift. I have D-Link DI-514 router which controlls two wired desktops. I am having a very hard time setting up a wireless connection.
 




I don't see anything under network settings in my control panel that helps with this.