OK - it sounds like you only need basic editing functionality.
There is a whole heap of MP3 editors out there - many of which are freeware or shareware. Here's a link:
Free mp3 editor downloads
I have to warn you that I can't vouch for any of these personally, though.
If I need to do any simple sound-file editing (and I can't be bothered to open FL Studio), I use GoldWave:
GoldWave - Audio Editing, Recording, Conversion, Restoration, & Analysis Software
I've got the full version, but I believe there's a fully-functioning demo version that you can download.