WinX Free MP4 to 3GP Converter is a free video converter. It is a good solution for conversion of MP4 files into the popular mobile format 3GP. The application will take standard-definition MP4 files as input, but it won't accept high-definition files or MP4 files encoded with special codecs. As far as output format support goes, this tool can convert files to either 3GP or MPEG-4 video files, using libamr_nb or AAC for audio.
Apart from being a great app because it is free and works well, this tool is also dead simple to use. When you first launch it, you will see on-screen help that guides you through the already simple conversion process. You simply load a file, select one of the supported formats and click on "Convert". The application will do the rest.
All in all, WinX Free MP4 to 3GP Converter does a good job of converting video files. It does, however, share a small problem with other WinX converters. By default, it is set to increase your audio volume. In the case of this app, the increase is only of 2 decibels, but other converters are set to 8 and 10. This can cause audio quality problems, so you might want to disable this by moving the slider down to 0.