Changing Audio Quality

[hugoharding]

How do I make a mp3 worse quality so that it has a smaller file size?

[nostalgia]

An existing mp3? Or do you want to make a mp3 (ripping)? Ripping audio tracks to mp3 is easy with a lot of programms nowadays. Cdex, Exact Audio Copy, dBpoweramp and so on. In all those programms you can choose which bitrate the mp3 has to have, so you can make it as small (bad sound) or big (good sound) as you want.

[4th gen]

DBpowerAMP (http://www.dbpoweramp.com) as suggested.