Windows 8 has the property of memory as the OS remembers the Wi-Fi profiles you connected to, earlier. The ugly part is these profiles pop up in the Wi-Fi network dialog even though you never wish to use them again.

Of course, you can remove the saved Wi-Fi Profiles by choosing "Forget this network" option by right clicking on a Wi-Fi Connection, but that is possible only when the network is in range.

So here's a command line util by Scott Hanselman to get rid of this problem. Visit Scott's blog to get the zipped version of this utility. It works on both, Windows 7 and Windows 8.