I use Audacity
(freeware), not Nero for processing audio. You can easily change the pitch, volume or speed of a sample (even sampling rate, e.g. 48 kHz from DAT to 44.1 kHz for CDs). To change the pitch, mark your sample and use the "Effect | Change pitch" dialog (with musical and physical options built in). To change volume, use "Effect | Amplify" or "Effect | Normalize".
Audacity can generate MP3 files directly with the Lame plugin.
@dodecahedron- I think you're refering to volume, not pitch.