i second audacity. but get the newest version it has better editing tools.
also remember that you need to import the audio each time you want to edit it if
you are doing more then one a day.
because opening a file with it will make audacity open a new instance of it each time it opens a new file.
so you would end up with as many of them open that you did editing of files.
it is an really intensive program so you need to follow all instructions on setting up the sound player's and the other settings.
in other words don't just run setup and try to use it like wmp.
but version 1.3 has a equalizer set up for editing that is very user friendly.
and a leveler feature that both compresses the peaks and rasies the volume.
and tons of other stuff that is fun to mess with.