WMP & WMC suddenly stopped playing my mp4 files

[satwar]

The good news is that my WM Extender still works fine and all my other PC's work fine playing these same mp4 with WMP & WMC. I have assumed that I've lost a vital codec but I've had no luck figuring out the problem codec.

Any suggestions on how to approach this problem ?

[Baldrick]

I hope you aren't running win98se....winxp?

Maybe just try install ffdshow.

[satwar]

Wow, I actually got it working again !!!

At first things got worse, and I couldn't play .avi files in addition to my original problem with only mp4 files. Internet Explorer and Windows Explorer were also starting to crash frequently.

First I applied MS Fix It for corrupt video codec causing crashes. Then I uninstalled all codec packs & programs. Then I ran a registry cleaner. Then I ran sfc /scannow. Then I installed codec packs (32 & 64 bit components because I have a x64 Win 7 PC). Remembering that everyone advises to do as little as possible when working with codec, I carefully read the installation guide and it said if you have mp4 problems disable Media Foundation on the 32 bit MP4 tab.

Bingo, both WMP & WMC play mp4 files perfectly.