Free Audio Editing Program.

Audacity is a free audio editing program which runs on Windows (Vista supported), MacOS, Linux, Unix. Easy to use interface, Having a dual core PC will also help.

Download Link:
http://audacity.sourceforge.net/







On the left is the programs main interface, logical layout of control buttons










File Loaded













And the list of plug-ins that you can play/twiddle with. Loads of options here.
















Audacity might not be the best looking piece of software ever made, but at least its functional, free and open source, so there will be updates.

Samples: