Audacity is an cross-platform audio editor and recorder. Audacity can record and play sounds and import and export WAV, AIFF, MP3, and OGG files. Edit your sounds using cut, copy, and paste features (with unlimited undo functionality), mix tracks, or apply effects to your recordings. Download Audacity Offline Installer Setup for Windows. Audacity also has a built-in amplitude-envelope editor, a customizable spectrogram mode, and a frequency-analysis window for audio-analysis applications. It comes with many useful features, some of which are:

Features:

Records and plays audio files
Supports various file formats like WAV, AIFF, AU, and Ogg Vorbis
Import MPEG audio (including MP2 and MP3 files)
Edit your audio files by cutting, copying, pasting, and mixing them
Large files can be edited fairly quickly
Add different effects like echo, phaser, wahwah, reverse, and more
Change the pitch without altering the tempo, or vice-versa.
Record and edit 16-bit, 24-bit, and 32-bit (floating point) samples.
Various plug-ins support
Can be used to convert old tapes into digital media
And many more.