Playing MP4 Files in XP
Windows XP's Windows Media Player 9, 10 and 11 will not play the MP4 file format. It can only play Windows media audio and video files extensions with aiff, asf, au, avi, midi, mp3, mpeg, wav, wmv and wma.
XP users will need a MP4 codec for Windows Media Player to view or listen to the MP4 file format. I have tried using the codec provided by Microsoft, but there's no luck in playing MP4 files after a successful installation on a XP computer. Fortunately, there is K-Lite Codec Pack, a third-party code package that you can install for XP so that you can play MP4 files without downloading another media player program.
Installing K-Lite codec pack is quite simple. Simply download any version of the codec pack from a free codecs website and save it on your desktop. Execute the downloaded file, e. g. K-Lite_Codec_Pack_700_Basic.exe, to install. You don't have to worry about the settings, but I suggest putting a check in the box before "Windows Media Player" when you see the file association option during installation: Proceed by clicking Next, and then click Select all video and Select all audio so you don't have to deal with the settings after the install process:
The icons for MP4 files that you have in Windows XP should now display the Windows Media Player icon on it: And you can now view MP4 files using Windows Media Player for XP!