Ah, I have Audacity (should have said, my puter's a Mac). Thanks very much. But could I ask for a little more help, please?

I'm importing the MP3 into Audacity. When I've done that, how do I make it louder?

Sorry to be such an ungeek; I'm a simple soul. Last week I watched six episodes of Heroes back-to-back because I couldn't get my neighbours' DVD player working and was lured into the evil toils of Channel 4.