I don't think DVD2OneX is what you are looking for.
Generally movies that you download are encoded as DIVX or some other MPEG-4 variant. DVD video needs to be MPEG-2.
The easiest way to do this is to re-encode the video into MPEG-2 with QuickTime Player and convert the audio into AC3. Then you can author a DVD using DVD Studio Pro.
I wouldn't expect the whole process to be worth the effort, considering how degraded the video quality will be.