How to volume level MPG?

Archived from groups: rec.video.desktop (More info?)

I often clip music from TV shows and play it back with a Media Player
playlist. The trouble is, Windows lets any application change the record
bus volume levels at any time and so my files get recorded at various,
intolerable, unpredictable, volume levels.

I want to fix the files I've already got. Is there a simple batch tool for
normalizing volume levels?

thanks for your advice.