OpenOffice batch Microsoft Office document converter
There is a lot of momentum behind the open XML document standards used in OpenOffice.org: OASIS, many governments around the world who want to protect the long term accessibility of their information, and just about anyone who has enough clue to not want to paint themselves into a corner with proprietary, patented, and changing-like-the-shifting-sands Microsoft document formats.
OpenOffice includes a batch mode document converter - I just used it today to convert 169 Word documents on my Mac to the open OOo file formats - easy!
The best solution is to refuse to use Microsoft products until they do the right thing by their customers: either declare free license use forever for WordML (a proprietary XML format with strange binary attachments), or adopt the technically superior (even without user extensibility) OOo XML formats.
The second best solution: if you must use Microsoft office, at least periodically auto-create OOo formated files, and back up these OOo files as part of your regular backup procedures.