To play an MP4 file on your PC, you need to have a player with this feature. If you are using version 12 of Windows Media Player will then be able to play MP4 Videos. If you have a previous version you should install a codec or use another player such as VLC or BS Player.
Part One - Using Default MP4 Players
1 - Select your video. Download the MP4 file from a trusted source, copy it from a USB drive or simply open it from your PC's hard drive. It is important to know the name of the file and its location. Click "File" and then "Open" and select the MP4 file you want.
2 - Double click on the video. Once you've found the video on your operating system, double-click the icon to start playing the MP4 file. If you double-click on the video file, playback will start using the default media player.
3 - Install a codec or decoder pack. Install the MPEG-4 decoder packs recommended by Microsoft, which are compatible with DirectShow. You can also download codecs from the link here.
4 - Right click on the video icon. If you are using Windows, you can right-click your file to select it instead of double-clicking half player of your choice.
5 - Click on "open with ..". From the menu that pops up you can choose any media you want.
6 - Click on Windows Media Player. If you've downloaded a decoder pack or codec then your MP4 video is ready to play.
Part two - Using other MP4 players
1 - Download a media player from a trusted source. Using other players may be more useful than installing codecs or decoder packs. Among the most popular player applications is VLC and XBMC.
2 - Go to Properties. Select another media player by going to Properties.
3 - Right click to select the media player. If you are using Windows, you can right-click your file instead of double-clicking to select the media player of your choice.
4 - Click on "open with ..". From the menu that pops up you can choose any media you want.
5 - Use an editor to play MP4 files. Most familiar users can use applications like Camtasia to edit the image and sound of a video. Professional DJs can also use Virtual DJ Pro as software that allows them to play videos.