Yes, you need to convert all your movies to a format iRiver and understand and play.
Here's a link:Movie Converter for iRiver and instructions
I'm not sure whether Movie Converter supports original DVD files. If that is not the case, then you'll have to convert DVD video into a format that iRiver X20 can use, and then feed that new video to Movie Converter.
However, that would be a bit redundant: to save on time and quality, you could use other video Conversion tools, such as SUPER:http://www.erightsoft.com/SUPER.html
After loading your DVD, you set the parameters to mirror those accepted by your iRiver model. In case of iRiver X20, those parameters are:
Extension: AVI [[also known as container]]
Video Codec: WMV9 SP, MPEG-4 SP [[MPEG-4 = XVID, DIVX]]
Video Resolution: max 320 × 240
Video Framerate: max 30 fps
Video Bit Rate: max 512 kbps
After successful conversion, upload your new video file to your iRiver X20 and play it back. If it plays [and plays correctly] - then congratulations - it works! If it does not play, then you might have made a mistake while setting the output parameters in SUPER.
Hope it helps. Rate me. Thanks.
.:: Cyberneticus ::.