The following codecs are supported in Windows Media Player for Windows XP:

- Cinepak codec
- ClearVideo Decoder Driver
- Fraunhofer IIS MPEG Layer-3 Codec
- Fraunhofer IIS MPEG Layer-3 Codec for MSACM
- Intel Audio Codec
- Intel I.263 Video Driver
- Intel Indeo 3.0 Video Codec
- Intel Indeo 5.0 Video Codec
- Intel Indeo(R) Video Interactive 32-bit Driver
- Intel RAW YVU9 Video Driver
- Lernout And Hauspie Codecs
- Microsoft MPEG-4 Standard Video Codec
- Microsoft MPEG-4 Video Codec v1
- Microsoft MPEG-4 Video Codec v2
- Microsoft MPEG-4 Video Codec v3
- Microsoft Network Audio CODEC
- Microsoft Screen Video Decompressor
- Microsoft Windows Media Video v7
- Microsoft Windows Media Video v8
- Sharp G.726 Audio Codec
- Sipro Lab Audio Telecom CODEC (Acelp)
- Streaming Animation Support
- Vivo H.263 Video CODEC
- Vivo Siren Audio CODEC
- VivoActive Audio CODEC
- Voxware MetaSound
- Voxware MetaVoice
- Windows Media Audio Codec

Note: Not all of the supported codecs are installed by default.