I found two good conversion software by accident
Pocket Video Converter, a powerful video converter for Pocket PC, Smart Phones, Palms, and more mobile devices. The Pocket Video Converter is capable of converting almost all popular video formats such as vob, DivX, XviD, MOV, rm, rmvb, MPEG, WMV, AVI to mobile device format(WMV、WMA、Mp3). All the conversion processes are very easy and fast with high quality.
you can get it here http://www.dvd-ripper-copy.com/pocket-video-converter.html
Also,Pocket DVD Ripper, the premiere video converter for movie lovers who want to watch popular videos anywhere and anytime.Comes with user-friendly interface and batch mode converting technology, you can easily and instantly convert DVD movies to WMV,WMA,MP3 format with high quality for your Pocket PC,Palm,Smartphones and other moblie devices.
you can try it here http://www.dvd-ripper-copy.com/pocket-dvd-ripper.html
And there is a bundle special offer called Pocket DVD Suite,which contains the two software above,http://www.dvd-ripper-copy.com/pocket-dvd-studio.html
maybe they are very useflul for you