You can't. Word 2000 has no such feature.

Word 2003 has a Research task pane that links to a translation Web service.
Without Word 2003, you can use the same Web service through Internet
Explorer:
http://www.worldlingo.com/en/product...ranslator.html or
you can use other translation sites such as http://babelfish.altavista.com.
Just copy the text from Word and paste it into the box on the site.

A warning: machine translation usually isn't good. Because it doesn't know
the meaning of your text, it just does substitutions and tries to patch up
the grammar. The results can be hilarious or embarrassing.

--
Regards,
Jay Freedman
Microsoft Word MVP FAQ: http://word.mvps.org