Mr Red wrote: Well all I can say is all the versions of Audacity I have installed on Windows, and there have been many up to about 1 year ago, lameenc.DLL had to be loaded separately.

In Linux, it depends on who packaged it - whether they included a dependency on the lame encoder (libmp3lame0) which depends whether the package is part of a 'pure opensource' distribution. But, as cnd said, if Audacity lacks a lame encoder it'll tell you. Lots of Linux software needs an mp3 encoder so any one of those could have caused it to be installed.

Stanron wrote: I spent some time today converting WAVs to MP3s to put on my MP3 player. It is slow but it is there.

If you don't mind using command line utilities, the easiest way to convert a WAV to and MP3 is ffmpeg:

ffmpeg -i filename.wav filename.mp3

I have a script for converting all files of a certain type in a directory to MP3 - I put a copy here.

Coming back to the original question, to slow down an audio to half speed can be done with:

ffmpeg -i inputfile -filter:a "atempo=0.5" outputfile