Copy Normal.dotm to %appdata%\Microsoft\Templates

More Info:

http://www.techrepublic.com/blog/windows-and-office/the-first-nine-things-i-do-to-default-settings-in-word-2013/

http://www.speakeasysolutions.com/blog/2009/11/26/modifying-word-2007-normal-dotm-template/