I downloaded an mp3 recording into my presentation - worked fine.  Then I revised mp3 - went to install voice recording - told it to delete original - clicked the check then tried to install new mp3 now when I run presentation I hear both recordings

The most likely reason is that you loaded one mp3 as a voiceover and the other as background music.

Try deleting both the voiceover track and the music track and then check that there is no sound at all before you import the mp3 that you want to use.

If that doesn't seem to be the case, you could try saving and closing your project and then closing and reopening videoscribe.