Word 2013 Operating in Compatibility Mode

Since you had Word 2010 installed when you installed Word 2013, you have an old version of Normal.dotm. Exit Word and then rename Normal.dotm as well as any left-over Normal.dot and similar files in your User Templates folder. Restart Word. You should get a factory default version of Normal which is in Word 2013 format.

This will be the folder which contains your normal.dotm file. See Normal Template in Microsoft Word - How to Find or Open the Normal Template.

Renaming rather than deleting is important because it may contain resources you will want to transfer to the new normal.dotm.

To see the exact path to the User Templates folder, you can make use of the File Locations dialog box. To open the dialog, click File | Options | Advanced and click the File Locations button.

Most likely, after you have installed a newer version of Office on top of an older one, you will find several renamed copies of older Normal templates (Normal1.dot, Normal1.dotm, etc.). Rename the file which is called Normal.dotm and just delete the other versions.