With nothing running, I would click on Start ' Run ' Type CMD to get to a Command Prompt.
From the Command Prompt, type sfc /scannow
This will run the Windows Resource Checker Version 6.0 program and it will verify All Windows files on your system are correct and not corrupted. At the end of the scan, if you get a message that indicates it could Not fix the problem, re-run the above command again.
The Other option is to download a program called MediaInfo. Once you install this program, it will allow you to right-click a Media File (.mpg, avi, mov, etc) and check to see details about the media file. You can download this Free program from address: https://mediaarea.net/en/MediaInfo
Another More useful program is something called the Sherlock Codec Detective. This Free program will tell you if your system has all of the required Codecs to play the file you are trying. You can download this Free program from address:
The File is located here:
So, after you install MediaInfo and see what the file contains in terms of Codecs, you use the Sherlock program to see if your system is missing any files that are required to play this. Anything missing will typically be shown in Reg under the column Video Codecs Installed (within Sherlock)
The "other" option is to download a Free program called the Media Player Codec Pack found at this address:
I would install either the Lite or Standard edition of the Codecs. I know some users will say Stay Away from Codecs, but since I found this Free program years ago, I can smoothly play DVD movies on my system. Please be aware that you should Backup your System before installing this Codec pack as it May over right a paid for Codec you might already have currently on your system.
This software is compatible with:
Microsoft Windows 10, 8.1, 8, 7, Vista, XP, 2000, 2008, & 2003
Microsoft Windows Media Player 12, 11 & 10
Any player compatible with DirectShow
The Last option I have is to make sure your Windows 7 system is up to date with installs. Do a manual check for updates and look under
the Optional Updates. If I remember correctly there was several patches/fixes from Microsoft to fix issues with the Media Player as well.
Best of Luck!