Thoughts before addressing your question (feel free to ignore):
- A document that you use every day? Unless this is some kind of journal, it should be a template. Templates in Microsoft Word
- I understand the idea of "if it ain't broke, don't fix it." However, Word 2000 was broke when it was put out by Microsoft, IMO. Office 2003 is a good stable version. If you do not want the learning curve of switching to the Ribbon UI, I suggest trying to find that. If going to the Ribbon, Office 2010 is quite good. I am using 365 and that has plusses and minuses.
Could you please attach two documents here? (One of them that has the problem style and a second that has the style the way you want it.)
Attach a Sample File Demonstrating the Problem - Here's How