To use the latest version of CoffeeCup HTML Editor, you must be using Windows XP Service Pack 3, Windows Vista, or Windows 7/8 with Internet Explorer 8.0 or higher.
If you are using a 64-bit version of any of these operating systems, the HTML Editor should work normally. If you experience any issues, consult this article: Is CoffeeCup Software Compatible With Windows 64-Bit?