I recently changed my wireless network connection now I don't know now to remove the old one. Help?

I recently changed my wireless connection to a new one because the previous one got hacked and became unsecured. I changed it using the same router as the previous one, but this one has a secure and complicated pword and has so far not been hacked. My issue is how do I remove the old network connection which still shows up in the wireless connection list that shows all of the wireless connections that are available. It is still showing as unsecured, and I would very much like to change that so that it is either secure or deleted. I have no intentions of using it again, but I would very much like it deleted. I have windows 7, so how would I go about doing this? Thanks.