Audacity.
You wanna cut compressed audio files, so of course Audacity or many other audio software titles will take some time to convert the audio to something lossless, even for just a cut.
I'm currently not at home, so I don't have access to some of my standard answers, but there is a poster which has a good quote on compression.
It goes like this: Imagine an empty can of soda. Step on it real hard so that it becomes flat. Now try to recreate the original shape of the can. You can't can you?
EDIT:
matteusclement:
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try this:
take an empty pop can, place it on the floor, smash it flat, now try to pull it back to how it was.
see how it looks like crap? that's call compression