Normal.dotm is the template upon which all new blank documents are based. It opens whenever you start Microsoft Office Word 2013 and it includes default styles and customizations that control the basic look of your document. Changes you make to Normal.dotm will be applied to documents that you create in the future.
In versions of Word prior to Word 2007, the Normal template used to be called normal.dot.
If you delete normal.dotm, the next time you open Word it will look for the file, and when it can’t find it Word will recreate the file in its original default condition. This means that the quickest way to reset all the quirky changes you have made to the Normal template is to delete normal.dotm. If you want to keep a version of the template just in case things go wrong, you can simply rename the file to something like normal_save.dotm. This file can then be reinstated later if things go pear shaped. Note that the file cannot be deleted or modified if Word has other documents open.
There are many ways to locate normal.dotm, but if you are in Word 2013, the easiest way is to click the File tab > Open > Computer > Browse.
Then, navigate to C:\Users\username\AppData\Roaming\Microsoft\Templates.
You should see Normal.dotm in the list.
Another way to get to the Template location is to click Start > Run > %appdata%\Microsoft\Templates\.
Reinstate Word 2003 Normal Template After Upgrade To Word 2013
By default, upgrading from Word 2003 to Word 2013 will have replaced the old Normal template with a new one. However, you may not want to lose all your old settings and you may want to reinstate your old Normal.dot. As part of the upgrade, your old Word 2003 template may have been renamed to something like Normal11.dot. Find it, rename it to Normal.dot and then delete the Word 2013 version (Normal.dotm). When Word next runs it will fail to find Normal.dotm in the Templates folder but will find Normal.dot instead, complete with all your old customizations. On exiting Word, it will re-create the new Normal.dotm using Normal.dot.