Rip audio from video files?

VLC can convert formats including extracting audio from video files and saving it as an MP3: https://wiki.videolan.org/Extract_audio/

It'd be easier to help, if you give some information on the video-/audio-format of your video files. You can use MediaInfoPortable for that or, if you use Media Player Classic as player, just hit Shift-F10 (thats basically an embedded MediaInfo).

Audacity will be able to use the audio from many more filetypes (including many videos) if it can find FFmpeg. Without it, it's unable to understand a lot of filetypes (especially videos).

To install FFmpeg for Audacity Portable:

1. Download the ffmpeg-win-2.2.2.zip file from http://lame.buanzo.org/#lamewindl
2. Extract all files to AudacityPortable\App\FFmpeg
3. Open Audacity Portable
4. Go to Edit > Preferences
5. Choose the "Libraries" section
6. Under "FFmpeg Import/Export Library" click "Locate"
7. It should tell you that FFmpeg has been "automatically located" and ask if you still want to locate it manually. If it does, select "No".
   If instead, it asks for a location, click "Browse…", and browse to AudacityPortable\App\FFmpeg, select avformat-55.dll, press "Open" & press "OK" in the "Locate FFmpeg" window.
8. Click OK to exit Audacity's Preferences window.