I just had a student asking me how to solve this problem. So to solve this problem (I found this answer in yahoo but it took a while to search so thats why I am posting it here):
1. Close Word.
2. Open Word.
3. Click the File tab on the Ribbon.
4. Click Open.
5. Select Templates in the Favorite Links pane.
6. Select Normal.dotm or Normal.dotx. (This may be just “Normal” also.) This should become your open document.
7. Now delete all the text in the document, including text in any headers and footers. Pressing CTRL/A followed by the Delete key is the fastest way to do this.
8. Save the file with CTRL/S. You may get a warning message about the Global template having been changed. This is OK. Click Yes.
9. Close Word.