Windows 8 Will Not Play MP4 Video
There are some issues with Windows 8 playing files.
Solution: Please make sure you have installed and recommend to your buyers that they install Windows 8 Media Player. To get the free download of Windows 8 Media Player, you need to install Windows 8 Pro, register for the Windows 8 Pro Pack through "Add Features to Windows 8" in the Control Panel, and then wait for Microsoft to send you a registration key by email.
There are some issues with Windows 8 playing files. According to this information:
It happened when Windows Vista replaced XP, and again when Windows 7 replaced Vista. Compatibility problems have cropped up again now that users are moving from Windows 7 to Windows 8, with many people complaining online that Windows 8 Media Player refused to play (or garbled) certain video files, or that the player got "hung" in its attempts at playback. Often, Windows 8 has issued error messages that "Windows Media Player cannot play this file."