This is viewing the webhelp locally (from the C: drive). I get the standard "Internet Explorer cannot open the webpage" message. Since posting I have uploaded a version of the help to my web site and this opens as expected on my windows 7 machine so obviously it is something to do with opening the files locally...but quite what???
In earlier browsers IE brought up a yellow information bar. There were two solutions. One was to generate with Mark of the Web, the other was to Allow Local Files to Run (or something like).
The first is in the wizard when you generate. Try that.
See www.grainge.org for RoboHelp and Authoring tips
Not sure quite why (I really don't get windows 7 at times) but moving the files (which I generated with mark of the web) from a shared public folder to the my documents folder has worked. Do I understand....No, and I bothered....Not especially!!!!
Thanks for the suggestions Peter - much appreciated.