A family of Microsoft word processing software products for creating web, email, and print documents.
Sorry, that was a slip of the fingers and lack of proofreading -- the shortcut for field codes is Alt+F9.
The Developer tab and Design Mode button have nothing to do with field codes. They display a different kind of tag, around different elements in the document (XML, content controls, and ActiveX controls). I mentioned them only as an alternative in case the field code setting didn't solve the problem.
The Compatibility Mode issue is a little difficult to explain.
- If the older files you referred to are in Word 97-2003 (*.doc) format, then Compatibility Mode is expected. That's the way Word is designed -- features that aren't supported by the older versions are disabled for these documents.
- If they're in Word 2007 (*.docx) format and were created in Word 2007, that suggests that until recently your Normal template was one that was created during an upgrade from a previous version, and was itself in Compatibility Mode. If that template was replaced because the old one was deleted or renamed, documents created since then would be not in Compatibility Mode. This scenario is extremely unlikely, because all the documents you created since installing 2007 would have had "Compatibility Mode" in the title bar, and I think you would have noticed that.
- You can convert any document from Compatibility Mode to regular mode by clicking the orb and selecting Convert. For details, read this article.