First of all, it is a Bog Standard Windows HTML Help File ... i.e. a
It's not an 'old style' Help File ... that went out with the advent
Windows 98 ... it's the 'new style', that has been COMPATIBLE since
I checked yesterday, and it IS compatible with Windows 7, and so I
assume it is also compatible with Vista, etc.
In any case, reading it, just requires a Windows Application ... but
it seems that Application - or, MORE LIKELY, "associations to
it" - may no longer be included in the latest versions
of Windows (for some reason ... I know not why).
However, the situation can be put right on either a Windows
Platform or a Mac Platform.
You may need to create and "association" with the Viewer Application
called hh.exe. You should find find hh.exe in Folder
Download & install from here: http://chmox.sourceforge.net/
And all should be well.