VLC – VideoLAN Media Player
VideoLAN VLC Media Player is a lightweight movie and music player that supports nearly any file format, and does NOT require the addition of any Codec, or driver files to make it work.
Some of the formats that VLC support are:
3GP,[17] ASF, AVI, FLV, MKV, Musical Instrument Digital Interface (.mid/.midi),[18] QuickTime, MP4, Ogg, OGM, WAV, MPEG-2 (ES, PS, TS, PVA, MP3), AIFF, Raw audio, Raw DV, MXF, VOB.
Video formats, Cinepak, Dirac, DV, H.263, H.264/MPEG-4 AVC, HuffYUV, Indeo 3,[19] MJPEG, MPEG-1, MPEG-2, MPEG-4 Part 2, RealVideo 3&4[20], Sorenson (thus enabling direct playback of the modified Sorenson H.263 encoded videos downloaded from YouTube), Theora, VC-1,[21] VP5,[21] VP6,[21] WMV, AAC, AC3, ALAC, AMR,[17] DTS, DV Audio, XM, FLAC, MACE, Mod, MP3, PLS, QDM2/QDMC, RealAudio,[23] Speex, Screamtracker 3/S3M, TTA, Vorbis, WavPack,[24] WMA.
the program also works amazingly well on a netbook, because it is so lightweight and it uses minimal system resources. The full package is just over 17MB, and is distributed as Open Source software, so you can also download and compile your own copy, if you want.
The FREE Windows version can be downloaded from here: http://www.videolan.org/vlc/download-windows.html