According to this post:
the conversion tool has been removed due to some GPL license issues.
There are a number of online audio file conversion tools and utilities available that Google or your search engine of choice should be able to find.
The Audio Converter is basically a gui interface for simplifing the conversions performed by three different utilities, they are LAME, SOX, and Voiceage g729 encoder/decoder. You will need to manually run the tools to get the correct file output. First step is to convert the file to a wave file this is where LAME is used. Next is to convert the wave file to the proper format which is 8000, ulaw,8 bit (G711) and 8000 signed-interger 16 bit (G729). And finally remove the wav header from the G729 file and adding the G729 header, this is done with Voiceage. Hopefully with this information and some research on each tool you will be able to get it figured out.
OK, reading between the lines, the licensing issues are probably related to G.729. If the OP can handle just G.711 then straight conversion to .wav monaural 8000, ulaw,8 bit should just work and there are numerous utilities to do that. For MOH, etc. try one of these:
Yesterday we uploaded a new version of the NetVanta Audio converter that has an alternative G729 encoder included. You can download it from this page on our main website:
Here is a link to our video detailing how to install this new version: [video] - Installing the NetVanta Audio Converter
The process is basically the same as past versions except now you omit the step for downloading the Voiceage G729 codec.
Message was edited by: matt - updated with link to video