Hi, my name’s Cody, and I’m working with the Windows Media Outreach Team to help answer questions folks might have about their copies of Windows Movie Maker.
Instead of just randomly downloading codecs with the hope that one of them works, I’d recommend downloading a codec tool that will analyze your particular video file and tell you exactly what codec(s) you’ll need to play the files.
Here are a couple of free tools that will do this for you: Gspot (http://www.headbands.com/gspot/) and Sherlock (http://www.updatexp.com/sherlock-codec-detective.html) Both of these work great, and using these on your file will tell you what codecs you need to get the particular file running properly, without making you download anything that you don’t need.
A lot of times codecs can conflict with one another, and overloading your system with a whole them is never a good idea, and having multiple amounts of them on your system can sometimes cause more more harm than good.
You also might want to check out this page: http://www.microsoft.com/windows/windowsmedia/player/faq/codec.mspx It’s a great guide to codecs that Microsoft has made available. It’ll also show you some trustworthy sites to download them from.
I hope this is helpful!
Thanks,
Cody
Windows Media Outreach Team