When you save a document in MS Word 2007 or higher, it is saved as a .docx document by default. However, if you want to share this document with someone who is using an older version of MS Word, you must save it in .doc format, otherwise they won’t be able to open the document.
If you want to save a document as .doc in Word 2007 only occasionally, then you can simply choose the file type in the save as dialog box, as shown in the image below.
However, if you have to always save the document in .doc format in Word 2007, then you may want to change the default document save format from .docx to .doc. Here’s the procedure,
1. Click on the Office icon, located on the top left corner. In the menu, click on Word Options button at bottom.
2. In the Word Options window, select Save in the left panel. Then choose Word 97-2003 Documents (*.doc) in the drop down and click OK.
That’s it. Now when you save any Word document, the default file type would be .doc.