An Estato forum member has written a free audio and video converter software for Windows PC that allows you to convert audio and video files optimized for Sony Ericsson UIQ3 based mobile devices like P990i/M600i as well as W950. The software claims to convert videos with 650kbit MPEG-4 @ 320×240 25fps, with 96kbit LC-AAC audio encoding using the XviD codec that gives DVD quality video playback on a Sony Ericsson PP990.
You can convert videos from mpeg/dat/avi/mp4/mov/flv/rmvb formats or even from an entire DVD . It can also convert audio files to mp3/aac/aac+/eaac+ formats for playback on the mobile device.

Download the Alpha version here