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)
- Improved: More miscellaneous UI/dialog tweaks & improvements
- Improved: Option to set the number of pixels to scroll for modern songticker
- Improved: [Gracenote/MusicID] Better error checking & memory cache optimizations
- Improved: [gen_ff] More miscellaneous freeform skinning engine optimizations
- Improved: [gen_hotkeys] Added optional WM_APPCOMMAND support for media keys
- Improved: [gen_hotkeys] Added increase + decrease rating on current track
- Improved: [in_dshow] Reading of length and bitrate for non-default video formats
- Improved: [in_flac] Optimized disk caching for increased performance
- Improved: [in_mp3] Better optimization for older Pentium Pro/2/3 cpu's
- Improved: [in_mp3] Support for reading ALBUM ARTIST field if TPE2 not present
- Improved: [in_mp4] Better Unicode support and metadata read optimizations
- Improved: [in_mp4] Optimized disk caching/reading
- Improved: [in_vorbis] Support for reading YEAR field if DATE not present
- Improved: [ml_disc/in_cdda] Disc reading tweaks and other general optimizations
- Improved: [ml_history] New tracking control options
- Improved: [ml_local] Album column sorting order logic
- Improved: [ml_local] Better playlist handling
- Improved: [ml_local] Bumped track# metadata guessing limit from 130 to 999
- Improved: [ml_local] Database query and memory optimizations
- Improved: [ml_pmp] Support for drag&drop from Explorer into portable device view
- Improved: [ml_transcode] Prompt to delete aborted transcodes
- Fixed: Artwork not found if .nfo filename contains a period
- Fixed: ASX Parser converting all stream links in .asx playlists to upper case
- Fixed: Classic songticker wraparound glitchiness
- Fixed: Global Hotkeys list destroyed when changing language packs
- Fixed: Gracenote/MusicID not using Winamp's proxy setting
- Fixed: Parsing of ansi ASX playlists containing non-standard characters
- Fixed: Restore from System Tray if previously closed in a minimized state
- Fixed: Setup resetting desktop icons :-o
- Fixed: Spectrum vis incompatibility crash with some 3rd-party input plugins
- Fixed: Truetype replacement font alignment in Winamp Modern winshade songticker
- Fixed: Various miscellaneous keyboard shortcut issues
- Fixed: Winamp Agent registry entry typo (wianmpa.exe)
- Fixed: [Bento] Collapse/Expand Playlist not respecting 'Show Album Art' setting
- Fixed: [gen_ff] Potential high CPU usage of songticker object
- Fixed: [gen_hotkeys] Restore from minimized state whilst About dialog is open
- Fixed: [gen_ml] Blank ML when restarting Winamp from a minimized state
- Fixed: [gen_ml] Cancelling Online Media password prompt clears password & filters
- Fixed: [in_dshow] Miscalculation of some mpeg video lengths
- Fixed: [in_flac] Divide-by-zero crash on corrupt files
- Fixed: [in_mp3] Deleting Lyrics3 tag in Alt+3 Editor also deletes ID3v1 tag
- Fixed: [in_mp3] Handling of ID3v2 with bad version/revision #'s
- Fixed: [in_mp3] ID3v2 parsing crash with some mp3's
- Fixed: [in_mp3] ID3v2 tag not showing when ID3v1 tag reading is disabled in config
- Fixed: [in_mp3] MPEG Info not showing in Alt+3 for files with large ID3v2 tags
- Fixed: [in_mp3] Now only reads first ID3v2 tag if more than one is present
- Fixed: [in_mp3] Winamp UI freezes when loading certain corrupt mp3's
- Fixed: [in_mp4] Playback of mp3 in mp4 container
- Fixed: [in_mp4] Seeking when paused
- Fixed: [in_mp4/jpeg.w5s] Crash when Art field is in metadata with no embedded art
- Fixed: [in_vorbis] UTF8->UTF16 optimized (fixes File Info delay bug)
- Fixed: [libmp4v2] Corrupt m4a's not playing, better handling of ones beyond repair
- Fixed: [ml_autotag] Stops processing when switching to another ml view
- Fixed: [ml_disc] CD view/titles not refreshing when ejecting old/inserting new CD
- Fixed: [ml_disc] Crash when using invalid strings in playlist filename generation
- Fixed: [ml_disc] No Burn button under some system configurations
- Fixed: [ml_disc/ml_pmp/ml_transcode] Processing of # in Destination Folder path
- Fixed: [ml_local] Artist column in descending order when sorting by Year
- Fixed: [ml_local] Down key in Search field not focusing the Simple View list
- Fixed: [ml_local] Last Updated, Album Gain & Podcast column sorting orders
- Fixed: [ml_playlists] Shift+Enter hotkey to Enqueue playlist
- Fixed: [ml_plg] Crash when stopping Playlist Generator scan or resetting database
- Fixed: [ml_pmp] Column sorting orders
- Fixed: [ml_rg] Restore from minimized state whilst rg results dialog is open
- Fixed: [ml_transcode] Restore from minimized state whilst config dialog is open
- Fixed: [ml_wire] Podcasts not being downloaded if
- Fixed: [ml_wire] Lockup when encountering scripts in field
- Fixed: [out_disk] Output folder always resetting to My Documents\My Music
- Fixed: [pmp_ipod] 'Add album art' option always checkmarked
- Fixed: [tataki] Potential crash when encountering an invalid/superficial error
- Techspot : a bunch of copy and paste idiots
- Misc: Alt+3 Auto-Tag now saves Gracenote FileId and ExtData fields
- Misc: Double-click Stereo indicator to open Playback prefs (Bento & Modern skins)
- Misc: Installation is now prevented on Win9x
- Misc: Split the Playback prefs into 3 tabs: Playback, Equalizer & Replay Gain
- Misc: Various installer setup & localization translation tweaks
- Misc: Various Bento skin fixes, tweaks and improvements
- Misc: Various Winamp Modern skin 5.5-related updates
- Misc: [ml_local] Removed deprecated 'Show album gain values' option in Prefs
- Updated: Bento skin #116
- Updated: libpng 1.2.22
- Updated: [vis_milk2] MilkDrop 2.0b