Windows Media Format 11 x86 (Windows XP x86 only)
Classic version of Windows Media Format 11, easy to find compared to the x64 version. Contains among others the WMV9 codecs, WMV9 Advanced Profile (VC-1) and WMA10 Pro. The WMV9 Advanced Profile codec supports the playback of interlaced wmv videos (Ex: 25fps read in 50Hz) and supports non-square pixels (useful for converting DVDs).

Windows Media Format 11 x64 (Windows XP x64 only)
Some of you may have noticed the Windows Media Player 11 for Windows XP x64 does not in fact have the latest Windows Media Format codecs. The installation program for installing WMP 11 x64 loads an obsolete version of these codecs, thus not allowing the playback of the WMA10 Pro 5.1 audio files (Surround).

The solution seems obvious, simply install the latest Windows Media Format 11 x64 codecs, but these are totally untraceable on the Net. There exists an updated version of the WMF 11 x64 codecs, situated on one of the latest discs of Visual Studio. I propose it to you in download.