Someone who won't mention his name on his comment suggested Audacity to edit the MP3. I took some of my time to download it and tried making the same ringtone as before. It's an open source project so it was within my area of interest anyway. Not to mention I have plenty of time to spare. :p
FYI, Audacity requires LAME MP3 Encoder library to be able to export an audio track to MP3 format. If you're interested in using Audacity, you can download LAME library from rarewares.org.
One key feature that I've come across during my short use of Audacity was its capability in mixing more than one audio tracks. I simply import the audio tracks that I want to mix and Audacity will show me separate audio tracks to edit instead of one already mixed audio tracks. That way I can easily modify each audio tracks without affecting the other. After I'm done with my modification, I can directly listen to the mixed result. When I'm satisfied with that result, exporting the mixed audio track was only a mouse click away. That is if I already have LAME MP3 Encoder.
When I'm using Music Editor Free, I can only mix more than one audio tracks. It won't be a problem if all the imported tracks were ready to be mixed. What happens when something was not right and I have to edit one of the tracks to be mixed? You can imagine how troublesome this could be if I were to go back and forth between editing a single track then tried mixing it with another audio track. So that's 1-0 for Audacity. :)
OK then. Before things get way to technical, I present you the result of mixing two copies of the first ringtone into a single audio track with a little time shift made to one of the track to add an echo effect. Mind you that this is coming from a beginner. So don't laugh, OK? ;)
You can download it here: http://www.4shared.com/file/80894398/316163a9/MichaelHeart_WeWillNotGoDown_Edit3.html
Many thanks to "Mr. I don't really know who" for directing me to Audacity.