GVC will help you convert your audio and video files using the FFMPEG codec via a simple and intuitive interface.
It is compatible with the most widely used video formats, and you can use it to extract the audio formats from films - great for making your own soundtracks, ring tones etc. The interface however is not simple for those that are not familiar with Visual Basic 2005 Express Edition. However, the good thing is that it's not that hard to learn and there are instructions with the program to help you get to grips with it. FFMPEG can decode (and convert) files of almost any format, including some rare formats such as game music files. You can convert any video file to the following format - AVI, ASF, MOV, MP4, 3GPP, 3GPP2, MPG, FLV, SWF, WMV, DV, OGG, MKV, RM. With audio, you can convert any audio file to the following formats - MP2, MP3, MP4, AIFF, FLAC, OGG, WMA, WAV, AC3, AMR. There's also the option to convert VCD .DAT files and DVD .VOB files to MPG. However for many it will be the audio extraction that is the most useful feature of this program and if only it was a bit simpler to use, it would be more popular.
The solid converter and audio extractor although you'll need to brush up your Visual Basic skills to use it.