Try FormatFactory (it's free) to convert media file types. I use this and apps from
Xilisoft also (but Xilisoft is not free)
FormatFactory - File format convert tools (http://www.formatoz.com)
FormatFactory is a multifunctional media converter.
All to MP4/3GP/MPG/AVI/WMV/FLV/SWF.
All to MP3//WMA/MMF/AMR/OGG/M4A/WAV.
All to JPG/BMP/PNG/TIF/ICO/....
Rip DVD to video file.
MP4 files support iPod/iPhone/PSP/
BlackBerry format.
Source files support RMVB.
FormatFactory's Feature:
1 support converting all popular video,audio,picture formats to others.
2 Repair damaged video and audio file.
3 Reducing Multimedia file size.
4 Support iphone,ipod multimedia file formats.
5 Picture converting supports Zoom,Rotate/Flip,tags.
6 DVD Ripper.