video is black, audio works fine

hello,

I recently downloaded windows movie maker 2012, which is a part of Windows Essentials on Windows 7.

I tried making a movie from the videos and music files I downloaded.

the format of the video files are mp4 and the format of the audio file is mp3.

the movie works fine in WMM itself.

but, if i try to save the movie and play it through media player, it doesn't seem to work.

i even tried converting the videos to wmv. format. but that didn't work either.

i saving it through various options like

*for computer

*for youtube

but none of them seem to work. please help me.

thank you