A good open source tool for converting even very complicated word documents is wvware.

From http://www.wvware.com:

wv is a library which allows access to Microsoft Word files. It can load and parse the word 2000, 97, 95 and 6 file formats.

Provided with the wv distributions is an application caled wvWare. wvWare is a "power-user" application with lots of command-line options, doo-dads, bells, and whistles. Less interesting, but more convenient are the helper scripts that utilize wvWare.

I've used this program myself for quite awhile, it's worth looking into.