Yes in RoboHelp for Word the source is a word document. The output is CHM. The formatting and styles used in Word are applied to the help file. Word 2010 is not supported in RoboHelp word, hence my query was posted in RobeHelp for word. As word 2010 is not listed under the options just like word 2003 and word 2007.
But RoboHelp for HTML supports word 2010, there aren't any issues with that.
Adobe (or Macromedia who owned RoboHelp before Abobe bought it) have not changed the RoboHelp for Word in a long, long time. As such if the documentation says that Word 2010 is not supported, it isn't. Your only option then is to use a supported Word version or go over to using RoboHelp HTML.
If you are producing a CHM file this is by far the best option. Why? For a start it uses actual HTML source code. RoboHelp for Word doesn't. It uses Word. It may well convert (very badly) the Word file into HTML but the result is widely accepted to be hopeless. As a result you are likely to get all sorts of issues.
It is your choice but producing CHM from the RoboHelp for Word application is like trying to run a 100 metre race whilst drinking a cup of coffee. It can be done but it will slow you up and make a lot of mess in the meantime 