Nullsoft Winamp is a fast, flexible, high-fidelity media player for Windows. Winamp supports playback of many audio (MP3, OGG, AAC, WAV, MOD, XM, S3M, IT, MIDI, etc) and video types (AVI, ASF, MPEG, NSV), custom appearances called skins (supporting both classic Winamp 1.x/2.x skins and Winamp 3 freeform skins), audio visualization and audio effect plug-ins (including two industry dominating visualization plug-ins), an advanced media library, Internet radio and TV support, CD ripping, and CD burning.

Changes in Winamp 5.51 :
- New: Autoplay Handlers for Audio, MP3 and Video CD's on WinXP & Vista
- New: Default Programs registration for installations on Windows Vista
- New: Optional Constant-Q Equalizer and optional ISO Standard frequency bands
- New: [in_flv] Flash Video decoder (vp6 only, not h.263)
- New: [ml_local] BPM column
- Improved: Browser download manager now uses CD Ripping destination folder
- Improved: Deletion of embedded album art via Artwork tab in File Info
- Improved: More accurately translated Language Packs (see note below)