HHSwitch.exe is a testing utility that allows you to switch between the various versions of HTML Help. This can be an essential tool if you want to be certain that your help files will work with different versions of HTML Help.
HHSwitch is free. You may download it and install it on as many machines as you want for no charge. The download size is around 2 megabytes, and it will expand to around 4 megabytes when installed. You must have Internet Explorer installed or the setup program won't run -- but you can download it with whatever browser you want. When you click the download link, you can either save it to disk and run it later, or just open it and have it run immediately.
Click download to begin.