There is a confusion whether 3Dfier works with DVD and the answer is obviously dependent on the media players that works with 3Dfier. And surely the Stereoscopic Player/3DVision Video Player can work with DVD and hence 3Dfier! Check out this page from 3dtv.at. It tells how DVD works with Stereoscopic Player.
If you use Media Player Classic, see here for the setting to make DVD works.