Convert Word Mail Merge documents from 2003 to 2010 format

I need to convert about 100 mail merge documents from 2003 to 2010 format(.doc to .docx).

The trouble I am having is that in order to convert the documents I need to open them. But some of them won't open because I don't have the correct header files/ any data in the files.

Is there a way I can convert these documents to the new format without opening them?

Note: The converter provided by microsoft fails. Also it doesn't matter how. If there's a program or code that can accompl开发者_开发百科ish this then it is helpful.

You can try npoi project.

Hope this helps.