FREE (Powerful) Sound Editor for XP
Audacity is a free audio editor. You can record sounds, play sounds, import and export WAV, AIFF, Ogg Vorbis, and MP3 files, and more. Use it to edit your sounds using Cut, Copy and Paste (with unlimited Undo), mix tracks together, or apply effects to your recordings.
It also has a built-in amplitude envelope editor, a customizable spectrogram mode and a frequency analysis window for audio analysis applications. Built-in effects include Echo, Change Tempo, and Noise Removal, and it also supports VST and LADSPA plug-in effects.
You can pick up your free copy of Audacity software here.
Using Audacity
Basics
Digital Audio
Rules of Audacity
Setup, Audio Import and Playback
Recording with Audacity
Editing for Beginners
Introduction to Editing...
Cut, Copy & Paste
Silence, Duplicate and Split
Splitting and Submixes
Common Editing Tasks
Quickies
Editing Vocal Tracks
Cutting up long Tracks
Effects for Beginners
Here are a couple more tutorials.
An Audacity 1.2 Tutorial by Dan Eliot. Covers opening an existing sound file, making simple edits, and exporting it again. Comes with Flash animations that walk you through everything in great detail!
An Audacity 1.0 Tutorial by Daniel James - comes with sample sound files for you to mix together. (excellent)
