Why can't I open an mp4 file?

Related questions

1. How can I play mp4 files on my computer?
2. How do I convert a m4a to mp3?
3. Can Windows 10 play mp4?
4. Why is Windows Media Player not playing mp4?
5. What plays mp4 files on Windows?
6. Can I convert m4a to mp3 in Windows Media Player?
7. How do I convert WAV to mp3 using Windows Media Player?
8. How do I convert mp4 files to play on Windows Media Player?
9. How do I convert m4a to mp3 on my laptop?
10. Why mp4 videos are not playing?

Tags

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2. #windows
3. #automatically
4. #video
5. #quicktime
6. #files
7. #favorite
8. #player
9. #already
10. #people
11. #install
12. #media
13. #since
14. #another
15. #mplayer
16. #should
17. #installed
18. #codec