There are lots of MP4 and WMV In-house videos which I’d like to larged watch in Windows Media Player. But I’m not sure why some of them failed to open in WMP. Could you help with that?

Maybe the files are corrupt? Perhaps you can try codec packs to experiment opening the files too.

This site can help: http://codecguide.com/index.html

Here is the wiki to help figure it out: en.wikipedia.org/wiki/K-Lite_Codec_Pack

Another wiki for codec type is this too: en.wikipedia.org/wiki/Combined_Community_Codec_Pack

I am no expert on this, but generally when WMP doesn't work out when opening files for various video types, I try Media Player Classic Home Cinema provided in the codec pack as an alternative. If this doesn't help, hopefully others can help out too who are more knowledgeable about opening video files.

To add to what shadowrgog said, both mp4 and wmv files are containers, and their streams (both audio and video) can be encoded with a variety of codecs. WMP uses the codecs that are installed in the system to play those files, and if it can't find a required codec, it cannot decode the file, thus some (if not all) parts of the file won't be played.

VLC and MPCHC both use built in codecs, and since they do include the most common ones, they can usually play most files immediately.

I was about to respond "dont bother - get VLC instead"

http://www.videolan.org/vlc/ I'd avoid codec packs - can cause some problems with various things (cannot be bothered to elaborate - sorry) - but thats what brought me to use VLC

It's a bit personal because when I was exploring finding video player alternatives to open various video files about 6 years ago I stumbled upon codec packs as an option as well as VLC. I didn't know anything about them so I just picked a codec pack option to try out first. As soon as I used it, it has worked all these years with no problems with files I wanted open. I think I used CCCP, but not sure anymore. Around the same time, a close friend of mine used VLC (I think for his mac) and had no problems opening video files too when we discussed our experiences with such options. I suppose experience varies from person to person. I am sure that when the day comes that if any problems should occur, alternatives are at the ready such as VLC.

true enough, but I (and plenty of others) found codec packs to cause problems outside of audio / video playing - ie with games. hence I suggest VLC

Right, such interplay with other forms of media like games is something I have no experience on (since I haven't had problems thus far), so I'll keep that in mind should problems could occur with regards to games. One thing I like, upon reading the wiki, is how easy it should be to uninstall something like CCCP if there are any issues. The first link in my first post suggests VLC player too if you look at the left hand side, real helpful when exploring options.

Aye true - think that was the last pack I used and uninstalled easily / clean enough as I remember (well, with a bit of ccleaner I think).

Just to reiterate. I'd recommend removing WMP completely from your computer and just use VLC media player.

the wmp player is designed for uninstallation

Just leave Windows Media Player where it is and download MPC HC. I recommend portable version - you won't need to install player nor any codecs packages on your system and you will be able to play all files you need.

I suggest forgetting about it and get VLC.

Someone send an AWAC to HQ ASAP before the VIPs see the URL and 86 our R&R, O.K.?

Get MPC-HC instead. VLC may play everything, but it is pretty bad at picture quality.