Remove Document Protection against Edit in Word 2007

I was trying to convert some case studies documents in SharePoint, to demonstrate that you are able to author content in Word, and publish them in HTML using document conversion process. But the document conversion process keep crashing because of certain elements in the Word document. But when I tried to edit, the document is protected against edit.

Knowing Word 2007 files are just xml files in a zip file, I did the following.

Rename the document to zip format
Open it up in my favorite zip program
Edit settings.xml in Notepad
Look for "protection" in the xml file, and you will locate <w:documentProtection> element.
Remove all the attributes in it.
Update the zip file
Rename the document back to docx
Open it up in Word 2007, and you are able to edit the document...