I know at least two guys who retired in their 30s after selling WinRAR-ish utilities for Windows. I also met someone selling a network scanning tool and making 900k a year. Another person I know wrote remote access tool and had, at his own admission, more money than he knew what to do with. All this was several years ago, when online sales were far less streamlined than they are now, social media and viral promoting were non-existent and they were selling shareware which was very actively cracked and pirated. Compare it to now, when you can buy software with one or two clicks, when users got conditioned into paying attention to digital signatures on .exe and real-time over-the-net licensing. It is obviously pointless to make any Windows software whatsoever.