inSSIDer was a great tool for scanning wireless networks on Windows, but the newest version has gone from open source to closed source. The For Home edition only allows for personal use and not business use (EULA doesn't state this currently, but contacting the company revealed they plan on changing the EULA).
Are there any alternatives that are free to use for personal or at work?
Windows 7 64-bit compatibility is required so NetStumbler is out.
I suppose one option would be to use inSSIDer version 2 which is still open source but no longer maintained. I'd expect that it will stop working eventually though.