Sometimes Word pops up with strange units of measurement which clutter the ruler with tiny divisions that bear no relationship to the preferred measurements set in Tools > Options > General. These are known as character units.
Character units above - centimeters required below:
This is an undesirable aspect of the Asian languages compatibility - undesirable for non-Asian languages that is. Fortunately the issue is soon fixed.
Press ALT+F11. This opens the macro editor. Press CTRL+G (View > Immediate Window). This provides a 'chat' window in which you can type vba code to be executed immediately. In that window, type
Options.UseCharacterUnit = False
and press the enter key.
Job done! You can now close the macro editor and return to Word, where you will find your chosen measurement option set - here centimeters.
This page only just made the cut to the new site as it applies primarily to Word 2002 and 2003 versions, and frankly it has been a while since I have seen the issue raised so it may have been fixed ... though somehow I doubt it.