Word 2007 will make an automatic backup copy for your documents unless you have turned off this option.  These files will be labeled with a file extension of .wbk 

To turn off the automatic backup option:

1. Click on the Microsoft Office Button
2. Click on Word Options located in the lower right hand corner of your screen.
3. Click on Advanced located on the left of your screen.
4. Scroll down until you see the Save section and uncheck the option that says Always create backup copy.
5. Click OK.