Porteus

For converting videos there is the famous ffmpeg, but without GUI.
Winff is a good GUI for ffmpeg but limited in options.
For Microsoft Windows there is MediaCoder a powerful tool to work with multiple video formats.
MediaCoder is functional in gnu/linux through wine.
I've done some tests here and this tool is working very well.

For wine download the version 32 bit.
http://www.mediacoderhq.com/