To add my two cents... (Euro zone, so not tuppence)
Smudger's idea of styles is by far the best approach.
If you get into the habit of writing with the style menu open (Format - Styles and Formatting), Word becomes a pretty useful tool for managing / synopsising your novel as well as automatically numbering your chapters. You simply select the most appropriate style for what you are writing.
For example, I have uploaded a template to here
http://www.gdcsoft.com/WW/NovelTemplate.zip. It has styles setup for act headings, chapter headings, characters, synopsis and manuscript. If you use styles as shown, then move the mouse over the table of contents and press F9, it will give you a pretty good map of your novel and allows you to compare the synopsis of what you actually wrote to what you had planned to write.
Comments welcome,
Gaius
<Added>Oops... for the technophobes amongst you who don't know how to unzip, I have also uploaded the .doc in unzipped format
here.