There're many cases that your MP4 files are not accepted by your MPEG supported players/devices. That's because MP4, referring to MPEG-4 as well, is not equal to MPEG (mainly MPEG-1 and MPEG-2) format. In order to make your computer, DVD player, video editing program, etc. able to handle the MP4 files, you need to convert MP4 to MPEG. To give an example, If you want to play MP4 video in a standalone DVD Player, to convert MP4 to MPEG-2 will be a great idea.
In regard of converting MP4 to MPG, a smart and professional MP4 to MPEG Converter is a must. Here, I recommend the one from Firecoresoft. Firecoresoft Video Converter is typically developed to help users convert videos from different format to format, including MP4 to MPEG (MPEG-1 and MPEG-2), with ultrafast conversion speed and superb output video quality. Now you can download the free trial version and follow the tutorial below to have a try.
After downloading and installing the MP4 to MPEG Converter, double click the icon to run it and then add the source MP4 files into it. Since the program is smart enough to detect the file types, you can just freely drag the select video files onto the program's standby list. Of course, you can also directly click the "Add Files" icon to locate the MP4 files from your media folders.
.mpg is the extension name of both MPEG-1 and MPEG-2 files. Hit the "Profile" menu bar and choose "MPEG-1" or "MPEG-2" codec from "Common Video" tab as the output format, then you would get MPG files flawlessly.
As the output format and parameters are well set, there's one more step you need to do: press the "START" button at the lower right of the main interface to launch the conversion from .mp4 to .mpg. When conversion is done, a pop-up window will indicate you the destination of the output files. Click "Yes" option to find these converted files.